Bump Microsoft.NET.Test.Sdk from 16.9.1 to 16.9.4

Bumps [Microsoft.NET.Test.Sdk](https://github.com/microsoft/vstest) from 16.9.1 to 16.9.4.
- [Release notes](https://github.com/microsoft/vstest/releases)
- [Commits](microsoft/vstest@v16.9.1...v16.9.4)

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

tests/Directory.Build.props

@@ -18,7 +18,7 @@
 		<PackageReference Include="AngleSharp.Diffing" Version="0.14.0" />
 		<PackageReference Include="AutoFixture" Version="4.15.0" />
 		<PackageReference Include="AutoFixture.Xunit2" Version="4.15.0" />
-		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />
+		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.4" />
 		<PackageReference Include="Moq" Version="4.16.1" />
 		<PackageReference Include="Shouldly" Version="4.0.3" />
 		<PackageReference Include="xunit" Version="2.4.1" />