Bump xunit.runner.visualstudio in /samples/snippets/csharp/xunit-test

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.8.0 to 2.8.1.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.8.0...2.8.1)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

samples/snippets/csharp/xunit-test/xunit-test.csproj

@@ -8,7 +8,7 @@
   <ItemGroup>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="xunit" Version="2.8.1" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.1" />
   </ItemGroup>
 
 </Project>