Bump xunit from 2.6.2 to 2.6.6 (#253)

Bumps [xunit](https://github.com/xunit/xunit) from 2.6.2 to 2.6.6.
- [Commits](xunit/xunit@2.6.2...2.6.6)

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

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

Author: dependabot[bot]

src/Directory.Build.targets

@@ -11,9 +11,9 @@
 	</ItemGroup>
 
 	<ItemGroup Condition="'$(IncludeTesting)' == 'true'">
-		<PackageReference Include="xunit" Version="2.6.2" />
-		<PackageReference Include="xunit.runner.visualstudio" Version="2.5.4" />
-		<PackageReference Include="xunit.runner.msbuild" Version="2.6.2" />
+		<PackageReference Include="xunit" Version="2.6.6" />
+		<PackageReference Include="xunit.runner.visualstudio" Version="2.5.6" />
+		<PackageReference Include="xunit.runner.msbuild" Version="2.6.6" />
 		<PackageReference Include="Moq" Version="4.18.4" />
 		<PackageReference Include="Newtonsoft.Json" Version="13.0.3" />
 	</ItemGroup>