Bump xunit from 2.4.2 to 2.6.4

Bumps [xunit](https://github.com/xunit/xunit) from 2.4.2 to 2.6.4.
- [Commits](xunit/xunit@2.4.2...2.6.4)

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

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

Tests/Directory.Build.props

@@ -8,7 +8,7 @@
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
     <PackageReference Include="Moq" Version="4.18.2" />
-    <PackageReference Include="xunit" Version="2.4.2" />
+    <PackageReference Include="xunit" Version="2.6.4" />
     <PackageReference Include="xunit.runner.visualstudio" PrivateAssets="all" Version="2.4.5">
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>