Bump FluentAssertions.Analyzers from 0.20.0 to 0.21.0 (#78)

Bumps [FluentAssertions.Analyzers](https://github.com/fluentassertions/fluentassertions.analyzers) from 0.20.0 to 0.21.0.
- [Release notes](https://github.com/fluentassertions/fluentassertions.analyzers/releases)
- [Commits](fluentassertions/fluentassertions.analyzers@0.20.0...v0.21.0)

---
updated-dependencies:
- dependency-name: FluentAssertions.Analyzers
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Directory.Build.props

@@ -62,7 +62,7 @@
 
   <ItemGroup Label="Test Projects" Condition="$(MSBuildProjectName.EndsWith('.Tests'))">
     <PackageReference Include="FluentAssertions" Version="6.11.0" />
-    <PackageReference Include="FluentAssertions.Analyzers" Version="0.20.0">
+    <PackageReference Include="FluentAssertions.Analyzers" Version="0.21.0">
       <PrivateAssets>all</PrivateAssets>
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>