Bump Microsoft.NET.Test.Sdk in /by-language/csharp-npgsql

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) from 17.12.0 to 17.13.0.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Changelog](https://github.com/microsoft/vstest/blob/main/docs/releases.md)
- [Commits](microsoft/vstest@v17.12.0...v17.13.0)

---
updated-dependencies:
- dependency-name: Microsoft.NET.Test.Sdk
  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 @@
   <ItemGroup>
     <PackageReference Include="Npgsql" Version="9.0.2" />
     <PackageReference Include="CommandLineParser" Version="2.9.1" />
-    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
+    <PackageReference Include="Microsoft.NET.Test.Sdk" Version="17.13.0" />
     <PackageReference Include="xunit" Version="2.9.3" />
     <PackageReference Include="xunit.runner.visualstudio" Version="3.0.1" />
     <PackageReference Include="coverlet.collector" Version="6.0.4" />