Bump Shouldly from 4.1.0 to 4.2.1

Bumps [Shouldly](https://github.com/shouldly/shouldly) from 4.1.0 to 4.2.1.
- [Release notes](https://github.com/shouldly/shouldly/releases)
- [Changelog](https://github.com/shouldly/shouldly/blob/master/BREAKING%20CHANGES.txt)
- [Commits](shouldly/shouldly@4.1.0...4.2.1)

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

Signed-off-by: dependabot[bot] <support@github.com>

Directory.Build.props

@@ -39,7 +39,7 @@
     <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="6.0.12" Condition="'$(TargetFramework)' == 'net6.0'" />
     <PackageReference Include="Microsoft.AspNetCore.TestHost" Version="7.0.4" Condition="'$(TargetFramework)' == 'net7.0'" />
     <PackageReference Include="Microsoft.Extensions.Configuration.Json" Version="7.0.0" />
-    <PackageReference Include="Shouldly" Version="4.1.0" />
+    <PackageReference Include="Shouldly" Version="4.2.1" />
     <PackageReference Include="NSubstitute" Version="5.0.0" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.4.1" />
     <PackageReference Include="xunit" Version="2.4.2" />