Bump log from 0.4.20 to 0.4.21 (#76)

Bumps [log](https://github.com/rust-lang/log) from 0.4.20 to 0.4.21.
<details>
<summary>Changelog</summary>
<p><em>Sourced from <a
href="https://github.com/rust-lang/log/blob/master/CHANGELOG.md">log's
changelog</a>.</em></p>
<blockquote>
<h2>[0.4.21] - 2024-02-27</h2>
<h2>What's Changed</h2>
<ul>
<li>Minor clippy nits by <a
href="https://github.com/nyurik"><code>@​nyurik</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/578">rust-lang/log#578</a></li>
<li>Simplify Display impl by <a
href="https://github.com/nyurik"><code>@​nyurik</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/579">rust-lang/log#579</a></li>
<li>Set all crates to 2021 edition by <a
href="https://github.com/nyurik"><code>@​nyurik</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/580">rust-lang/log#580</a></li>
<li>Various changes based on review by <a
href="https://github.com/Thomasdezeeuw"><code>@​Thomasdezeeuw</code></a>
in <a
href="https://redirect.github.com/rust-lang/log/pull/583">rust-lang/log#583</a></li>
<li>Fix typo in file_static() method doc by <a
href="https://github.com/dimo414"><code>@​dimo414</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/590">rust-lang/log#590</a></li>
<li>Specialize empty key value pairs by <a
href="https://github.com/EFanZh"><code>@​EFanZh</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/576">rust-lang/log#576</a></li>
<li>Fix incorrect lifetime in Value::to_str() by <a
href="https://github.com/peterjoel"><code>@​peterjoel</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/587">rust-lang/log#587</a></li>
<li>Remove some API of the key-value feature by <a
href="https://github.com/Thomasdezeeuw"><code>@​Thomasdezeeuw</code></a>
in <a
href="https://redirect.github.com/rust-lang/log/pull/585">rust-lang/log#585</a></li>
<li>Add logcontrol-log and log-reload by <a
href="https://github.com/swsnr"><code>@​swsnr</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/595">rust-lang/log#595</a></li>
<li>Add Serialization section to kv::Value docs by <a
href="https://github.com/Thomasdezeeuw"><code>@​Thomasdezeeuw</code></a>
in <a
href="https://redirect.github.com/rust-lang/log/pull/593">rust-lang/log#593</a></li>
<li>Rename Value::to_str to to_cow_str by <a
href="https://github.com/Thomasdezeeuw"><code>@​Thomasdezeeuw</code></a>
in <a
href="https://redirect.github.com/rust-lang/log/pull/592">rust-lang/log#592</a></li>
<li>Clarify documentation and simplify initialization of
<code>STATIC_MAX_LEVEL</code> by <a
href="https://github.com/ptosi"><code>@​ptosi</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/594">rust-lang/log#594</a></li>
<li>Update docs to 2021 edition, test by <a
href="https://github.com/nyurik"><code>@​nyurik</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/577">rust-lang/log#577</a></li>
<li>Add &quot;alterable_logger&quot; link to README.md by <a
href="https://github.com/brummer-simon"><code>@​brummer-simon</code></a>
in <a
href="https://redirect.github.com/rust-lang/log/pull/589">rust-lang/log#589</a></li>
<li>Normalize line ending by <a
href="https://github.com/EFanZh"><code>@​EFanZh</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/602">rust-lang/log#602</a></li>
<li>Remove <code>ok_or</code> in favor of <code>Option::ok_or</code> by
<a
href="https://github.com/AngelicosPhosphoros"><code>@​AngelicosPhosphoros</code></a>
in <a
href="https://redirect.github.com/rust-lang/log/pull/607">rust-lang/log#607</a></li>
<li>Use <code>Acquire</code> ordering for initialization check by <a
href="https://github.com/AngelicosPhosphoros"><code>@​AngelicosPhosphoros</code></a>
in <a
href="https://redirect.github.com/rust-lang/log/pull/610">rust-lang/log#610</a></li>
<li>Get structured logging API ready for stabilization by <a
href="https://github.com/KodrAus"><code>@​KodrAus</code></a> in <a
href="https://redirect.github.com/rust-lang/log/pull/613">rust-lang/log#613</a></li>
</ul>
<h2>New Contributors</h2>
<ul>
<li><a href="https://github.com/nyurik"><code>@​nyurik</code></a> made
their first contribution in <a
href="https://redirect.github.com/rust-lang/log/pull/578">rust-lang/log#578</a></li>
<li><a href="https://github.com/dimo414"><code>@​dimo414</code></a> made
their first contribution in <a
href="https://redirect.github.com/rust-lang/log/pull/590">rust-lang/log#590</a></li>
<li><a href="https://github.com/peterjoel"><code>@​peterjoel</code></a>
made their first contribution in <a
href="https://redirect.github.com/rust-lang/log/pull/587">rust-lang/log#587</a></li>
<li><a href="https://github.com/ptosi"><code>@​ptosi</code></a> made
their first contribution in <a
href="https://redirect.github.com/rust-lang/log/pull/594">rust-lang/log#594</a></li>
<li><a
href="https://github.com/brummer-simon"><code>@​brummer-simon</code></a>
made their first contribution in <a
href="https://redirect.github.com/rust-lang/log/pull/589">rust-lang/log#589</a></li>
<li><a
href="https://github.com/AngelicosPhosphoros"><code>@​AngelicosPhosphoros</code></a>
made their first contribution in <a
href="https://redirect.github.com/rust-lang/log/pull/607">rust-lang/log#607</a></li>
</ul>
</blockquote>
</details>
<details>
<summary>Commits</summary>
<ul>
<li><a
href="https://github.com/rust-lang/log/commit/3ccdc286fef3076747fe18a2a93658ea4d4ae012"><code>3ccdc28</code></a>
Merge pull request <a
href="https://redirect.github.com/rust-lang/log/issues/617">#617</a>
from rust-lang/cargo/0.4.21</li>
<li><a
href="https://github.com/rust-lang/log/commit/6153cb289f0e7b80f00ae07dbe5ee41cf3d3fcb0"><code>6153cb2</code></a>
prepare for 0.4.21 release</li>
<li><a
href="https://github.com/rust-lang/log/commit/f0f74946a4bfb02cfc407795a3499c4b69d7a290"><code>f0f7494</code></a>
Merge pull request <a
href="https://redirect.github.com/rust-lang/log/issues/613">#613</a>
from rust-lang/feat/kv-cleanup</li>
<li><a
href="https://github.com/rust-lang/log/commit/2b220bf3b705f2abc0ee591c7eb17972a979da3a"><code>2b220bf</code></a>
clean up structured logging example</li>
<li><a
href="https://github.com/rust-lang/log/commit/646e9ab9917fb79e44b6b36b8375106a1a09766c"><code>646e9ab</code></a>
use original Visitor name for VisitValue</li>
<li><a
href="https://github.com/rust-lang/log/commit/cf85c38d3519745d60e7b891c4b2025050a8389f"><code>cf85c38</code></a>
add needed subfeatures to kv_unstable</li>
<li><a
href="https://github.com/rust-lang/log/commit/73e953905b970ef765a86bf6cbd69bc2c5e2bac4"><code>73e9539</code></a>
fix up capturing of :err</li>
<li><a
href="https://github.com/rust-lang/log/commit/31bb4b0ff36e458c6bef304a336b71f6342ddcc7"><code>31bb4b0</code></a>
move error macros together</li>
<li><a
href="https://github.com/rust-lang/log/commit/ad917118a5e781d0dd60b3a75ba519ce9839ba70"><code>ad91711</code></a>
support field shorthand in macros</li>
<li><a
href="https://github.com/rust-lang/log/commit/90a347bd836873264a393a35bfd90fe478fadae2"><code>90a347b</code></a>
restore removed APIs as deprecated</li>
<li>Additional commits viewable in <a
href="https://github.com/rust-lang/log/compare/0.4.20...0.4.21">compare
view</a></li>
</ul>
</details>
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