Bump Polyfill from 7.14.0 to 7.15.0 in /src (#484)

Author: dependabot[bot]

src/Directory.Packages.props

@@ -7,7 +7,7 @@
     <PackageVersion Include="Bogus" Version="35.6.1" />
     <PackageVersion Include="MarkdownSnippets.MsBuild" Version="27.0.2" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
-    <PackageVersion Include="Polyfill" Version="7.14.0" />
+    <PackageVersion Include="Polyfill" Version="7.15.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.147" />
     <PackageVersion Include="System.CodeDom" Version="9.0.1" />
     <PackageVersion Include="System.Net.Http" Version="4.3.4" />