Update dependency microsoft.testing.platform.msbuild to 1.9.0 (#358)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

Author: renovate[bot]

Directory.Packages.props

@@ -20,7 +20,7 @@
     <PackageVersion Include="Microsoft.CodeAnalysis.VisualBasic" Version="$(CodeAnalysisVersion)" />
     <PackageVersion Include="Microsoft.CodeAnalysis.VisualBasic.CodeFix.Testing.XUnit" Version="$(CodefixTestingVersion)" />
     <PackageVersion Include="Microsoft.IO.Redist" Version="6.1.0" />
-    <PackageVersion Include="microsoft.testing.platform.msbuild" Version="1.8.4" />
+    <PackageVersion Include="microsoft.testing.platform.msbuild" Version="1.9.0" />
     <PackageVersion Include="Microsoft.VisualStudio.Composition" Version="17.12.20" />
     <PackageVersion Include="Microsoft.VisualStudio.Interop" Version="17.13.40008" />
     <PackageVersion Include="Microsoft.VisualStudio.RpcContracts" Version="17.13.7" />