refs and cleanup

Author: SimonCropp

src/Directory.Packages.props

@@ -6,7 +6,7 @@
   <ItemGroup>
     <PackageVersion Include="MarkdownSnippets.MsBuild" Version="28.0.0-beta.7" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
-    <PackageVersion Include="Polyfill" Version="9.0.3" />
+    <PackageVersion Include="Polyfill" Version="9.1.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.162" />
     <PackageVersion Include="System.Text.Json" Version="10.0.0" />
     <PackageVersion Include="Verify" Version="31.7.1" />