Bump Microsoft.TestPlatform.ObjectModel from 16.9.1 to 16.9.4

Bumps [Microsoft.TestPlatform.ObjectModel](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-preview[bot] <[email protected]>

Author: dependabot-preview[bot]

Tests/Directory.Build.props

@@ -7,7 +7,7 @@
       <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
     </PackageReference>
     <PackageReference Include="Microsoft.NET.Test.Sdk" Version="16.9.1" />
-    <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="16.9.1" />
+    <PackageReference Include="Microsoft.TestPlatform.ObjectModel" Version="16.9.4" />
     <PackageReference Include="Moq" Version="4.16.1" />
     <PackageReference Include="xunit" Version="2.4.1" />
     <PackageReference Include="xunit.runner.visualstudio" PrivateAssets="All" Version="2.4.3">