Bump Polyfill from 2.4.0 to 2.6.5 in /src

Bumps [Polyfill](https://github.com/SimonCropp/Polyfill) from 2.4.0 to 2.6.5.
- [Commits](https://github.com/SimonCropp/Polyfill/commits)

---
updated-dependencies:
- dependency-name: Polyfill
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

src/MarkdownSnippets/MarkdownSnippets.csproj

@@ -5,7 +5,7 @@
   </PropertyGroup>
   <ItemGroup>
     <PackageReference Include="ProjectDefaults" Version="1.0.110" PrivateAssets="all" />
-    <PackageReference Include="Polyfill" Version="2.4.0" PrivateAssets="all" />
+    <PackageReference Include="Polyfill" Version="2.6.5" PrivateAssets="all" />
     <PackageReference Include="System.Memory" Version="4.5.5" Condition="'$(TargetFrameworkIdentifier)' == '.NETStandard' OR '$(TargetFrameworkIdentifier)' == '.NETFramework' OR '$(TargetFrameworkIdentifier)' == '.NETCOREAPP'" />
   </ItemGroup>
 </Project>