Bump Polyfill from 7.5.0 to 7.8.0

Bumps [Polyfill](https://github.com/SimonCropp/Polyfill) from 7.5.0 to 7.8.0.
- [Commits](SimonCropp/Polyfill@7.5.0...7.8.0)

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

Signed-off-by: dependabot[bot] <[email protected]>

src/Directory.Build.props

@@ -29,7 +29,7 @@
 
   <ItemGroup>
     <PackageReference Include="ConfigureAwaitChecker.Analyzer" Version="5.0.0.1" PrivateAssets="All" />
-    <PackageReference Include="Polyfill" Version="7.5.0" PrivateAssets="All" />
+    <PackageReference Include="Polyfill" Version="7.8.0" PrivateAssets="All" />
   </ItemGroup>
 
   <ItemGroup>