chore(deps): update dependency xunit to v2.6.6

Author: renovate[bot]

test/Directory.Build.props

@@ -10,7 +10,7 @@
     <ItemGroup>
         <PackageReference Include="FluentAssertions" Version="6.12.0" />
         <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.8.0" />
-        <PackageReference Include="xunit" Version="2.6.5" />
+        <PackageReference Include="xunit" Version="2.6.6" />
         <PackageReference Include="xunit.runner.visualstudio" Version="2.5.6">
             <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
             <PrivateAssets>all</PrivateAssets>