Update dependency microsoft.testing.platform.msbuild to 1.9.1

Author: renovate[bot]

Directory.Packages.props

@@ -12,7 +12,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageVersion Include="Microsoft.IO.Redist" Version="6.1.0" />
-    <PackageVersion Include="microsoft.testing.platform.msbuild" Version="1.9.0" />
+    <PackageVersion Include="microsoft.testing.platform.msbuild" Version="1.9.1" />
     <PackageVersion Include="Microsoft.CodeAnalysis.PublicApiAnalyzers" Version="$(MicrosoftCodeAnalysisAnalyzersVersion)" />
     <PackageVersion Include="Microsoft.VisualStudio.Composition" Version="17.12.20" />
     <PackageVersion Include="Microsoft.VisualStudio.Interop" Version="17.13.40008" />