Bump Polyfill from 7.12.0 to 7.13.0 in /src (#273)

Author: dependabot[bot]

src/Directory.Packages.props

@@ -6,7 +6,7 @@
   <ItemGroup>
     <PackageVersion Include="MarkdownSnippets.MsBuild" Version="27.0.2" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
-    <PackageVersion Include="Polyfill" Version="7.12.0" />
+    <PackageVersion Include="Polyfill" Version="7.13.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.147" />
     <PackageVersion Include="System.Text.Json" Version="9.0.1" />
     <PackageVersion Include="Verify" Version="28.9.0" />