Bump the tests group with 2 updates

Bumps the tests group with 2 updates: [xunit](https://github.com/xunit/xunit) and [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit).


Updates `xunit` from 2.5.0 to 2.6.2
- [Commits](xunit/xunit@2.5.0...2.6.2)

Updates `xunit.runner.visualstudio` from 2.5.0 to 2.5.4
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.0...2.5.4)

---
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-patch
  dependency-group: tests
...

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

src/ThisAssembly.Tests/ThisAssembly.Tests.csproj

@@ -39,8 +39,8 @@
     <PackageReference Include="PolySharp" Version="1.13.2" PrivateAssets="All" />
     <PackageReference Include="Microsoft.CodeAnalysis.CSharp" Version="4.0.1" Pack="false" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
-    <PackageReference Include="xunit" Version="2.5.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.0" />
+    <PackageReference Include="xunit" Version="2.6.2" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.4" />
   </ItemGroup>
 
   <ItemGroup>