refs and cleanup

Author: SimonCropp

src/Directory.Packages.props

@@ -9,7 +9,7 @@
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp" Version="4.9.2" Pinned="true" />
     <PackageVersion Include="Microsoft.CodeAnalysis.VisualBasic" Version="4.9.2" Pinned="true" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
-    <PackageVersion Include="Polyfill" Version="9.3.2" />
+    <PackageVersion Include="Polyfill" Version="9.3.4" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.163" />
     <PackageVersion Include="Verify" Version="31.8.0" />
     <PackageVersion Include="Verify.DiffPlex" Version="3.1.2" />