Bump the testing group with 4 updates

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


Updates `Microsoft.NET.Test.Sdk` from 17.7.1 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@v17.7.1...v17.8.0)

Updates `Verify.Xunit` from 20.8.1 to 20.8.2
- [Release notes](https://github.com/VerifyTests/Verify/releases)
- [Commits](VerifyTests/Verify@20.8.1...20.8.2)

Updates `xunit` from 2.5.0 to 2.6.6
- [Commits](xunit/xunit@2.5.0...2.6.6)

Updates `xunit.runner.visualstudio` from 2.5.0 to 2.5.6
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.0...2.5.6)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: testing
- dependency-name: Verify.Xunit
  dependency-type: direct:production
  update-type: version-update:semver-patch
  dependency-group: testing
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
  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]>

Author: dependabot[bot]

test/Tests.csproj

@@ -41,7 +41,7 @@
     <PackageReference Include="System.IO.Abstractions.TestingHelpers" Version="19.2.69" />
     <PackageReference Include="Verify.Xunit" Version="20.8.1" />
     <PackageReference Include="xunit" Version="2.5.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.0">
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.6">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
       <PrivateAssets>all</PrivateAssets>
     </PackageReference>