Bump the testing group with 4 updates

Bumps the testing group with 4 updates: [FakeItEasy](https://github.com/FakeItEasy/FakeItEasy), [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest), [xunit](https://github.com/xunit/xunit) and [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit).


Updates `FakeItEasy` from 7.4.0 to 8.1.0
- [Release notes](https://github.com/FakeItEasy/FakeItEasy/releases)
- [Commits](FakeItEasy/FakeItEasy@7.4.0...8.1.0)

Updates `Microsoft.NET.Test.Sdk` from 17.7.2 to 17.8.0
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Changelog](https://github.com/microsoft/vstest/blob/main/docs/releases.md)
- [Commits](microsoft/vstest@v17.7.2...v17.8.0)

Updates `xunit` from 2.6.1 to 2.6.6
- [Commits](xunit/xunit@2.6.1...2.6.6)

Updates `xunit.runner.visualstudio` from 2.5.3 to 2.5.6
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.3...2.5.6)

---
updated-dependencies:
- dependency-name: FakeItEasy
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: testing
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: testing
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: testing
- dependency-name: xunit.runner.visualstudio
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: testing
...

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

test/TailwindCssTagHelpersTests.csproj

@@ -24,7 +24,7 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
     <PackageReference Include="Shouldly" Version="4.2.1" />
     <PackageReference Include="xunit" Version="2.6.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.3">
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.6">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>