Bump xunit from 2.8.1 to 2.9.0 in /by-language/csharp-npgsql

Bumps xunit from 2.8.1 to 2.9.0.

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

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

Author: dependabot[bot]

by-language/csharp-npgsql/demo.csproj

@@ -12,7 +12,7 @@
     <PackageReference Include="Npgsql" Version="8.0.3" />
     <PackageReference Include="CommandLineParser" Version="2.9.1" />
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.10.0" />
-    <PackageReference Include="xunit" Version="2.8.1" />
+    <PackageReference Include="xunit" Version="2.9.0" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.8.2" />
     <PackageReference Include="coverlet.collector" Version="6.0.2" />
   </ItemGroup>