build(deps): bump xunit from 2.5.1 to 2.6.0 in /src (#583)

Bumps [xunit](https://github.com/xunit/xunit) from 2.5.1 to 2.6.0.
- [Commits](xunit/xunit@2.5.1...2.6.0)

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

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

src/ReactiveUI.Validation.Tests/ReactiveUI.Validation.Tests.csproj

@@ -11,7 +11,7 @@
 
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.7.2" />
-    <PackageReference Include="xunit" Version="2.5.1" />
+    <PackageReference Include="xunit" Version="2.6.0" />
     <PackageReference Include="Xunit.StaFact" Version="1.1.11" />
     <PackageReference Include="Microsoft.Reactive.Testing" Version="6.0.0" />
     <PackageReference Include="PublicApiGenerator" Version="11.0.0" />