Bump the tests group with 3 updates

Bumps the tests group with 3 updates: [xunit](https://github.com/xunit/xunit), [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) and [Microsoft.TestPlatform.ObjectModel](https://github.com/microsoft/vstest).


Updates `xunit` from 2.4.2 to 2.7.0
- [Commits](xunit/xunit@2.4.2...2.7.0)

Updates `xunit.runner.visualstudio` from 2.4.5 to 2.5.7
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@v2.4.5...2.5.7)

Updates `Microsoft.TestPlatform.ObjectModel` from 17.4.1 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@v17.4.1...v17.8.0)

---
updated-dependencies:
- dependency-name: xunit
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: tests
- dependency-name: xunit.runner.visualstudio
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: tests
- dependency-name: Microsoft.TestPlatform.ObjectModel
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: tests
...

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

src/NuDoq.Tests/NuDoq.Tests.csproj

@@ -15,8 +15,8 @@
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.4.1" />
     <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="17.4.1" />
     <PackageReference Include="System.Net.Http" Version="4.3.4" />
-    <PackageReference Include="xunit" Version="2.4.2" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.4.5" />
+    <PackageReference Include="xunit" Version="2.7.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.7" />
   </ItemGroup>
 
   <ItemGroup>