Bump Microsoft.NET.Test.Sdk from 16.9.1 to 16.9.4 (#86)

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>

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

(skip release)

test/dotnet-serve.Tests/dotnet-serve.Tests.csproj

@@ -28,7 +28,7 @@
   <ItemGroup>
     <PackageReference Include="coverlet.collector" Version="3.0.3" />
     <PackageReference Include="McMaster.Extensions.XUnit" Version="0.1.0" />
-    <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="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" Version="2.4.3" />