refs and cleanup

Author: SimonCropp

src/Directory.Packages.props

@@ -6,7 +6,7 @@
   <ItemGroup>
     <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.2" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.4.0" />
-    <PackageVersion Include="Polyfill" Version="10.0.0" />
+    <PackageVersion Include="Polyfill" Version="10.1.1" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.172" />
     <PackageVersion Include="Verify" Version="31.15.0" />
     <PackageVersion Include="Verify.DiffPlex" Version="3.1.2" />