Bump Polyfill from 6.5.0 to 6.8.0

Bumps [Polyfill](https://github.com/SimonCropp/Polyfill) from 6.5.0 to 6.8.0.
- [Commits](SimonCropp/Polyfill@6.5.0...6.8.0)

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

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

src/Directory.Packages.props

@@ -14,7 +14,7 @@
     <PackageVersion Include="Microsoft.CodeAnalysis.CSharp.SourceGenerators.Testing.XUnit" Version="1.1.2" />
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.11.1" />
     <PackageVersion Include="Microsoft.SourceLink.GitHub" Version="8.0.0" />
-    <PackageVersion Include="Polyfill" Version="6.5.0" />
+    <PackageVersion Include="Polyfill" Version="6.8.0" />
     <PackageVersion Include="Verify.SourceGenerators" Version="2.4.1" />
     <PackageVersion Include="Verify.Xunit" Version="26.4.4" />
     <PackageVersion Include="xunit" Version="2.9.0" />