Update sphinx requirement from ~=4.4 to ~=5.0 in /requirements (palle…

…ts-eco#626)

Updates the requirements on [sphinx](https://github.com/sphinx-doc/sphinx) to permit the latest version.
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/5.x/CHANGES)
- [Commits](sphinx-doc/sphinx@v4.4.0...v5.0.0)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

requirements/docs.txt

@@ -1,3 +1,3 @@
 Pallets-Sphinx-Themes~=2.0
-Sphinx~=4.4
+Sphinx~=5.0
 sphinx-issues==3.0.1