Bump xunit.runner.visualstudio in /by-language/csharp-npgsql

Bumps [xunit.runner.visualstudio](https://github.com/xunit/visualstudio.xunit) from 2.5.8 to 2.8.0.
- [Release notes](https://github.com/xunit/visualstudio.xunit/releases)
- [Commits](xunit/visualstudio.xunit@2.5.8...2.8.0)

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

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

by-language/csharp-npgsql/demo.csproj

@@ -13,7 +13,7 @@
     <PackageReference Include="CommandLineParser" Version="2.9.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.9.0" />
     <PackageReference Include="xunit" Version="2.8.0" />
-    <PackageReference Include="xunit.runner.visualstudio" Version="2.5.8" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="2.8.0" />
     <PackageReference Include="coverlet.collector" Version="6.0.2" />
   </ItemGroup>