[main] Bump Polyfill from 7.5.0 to 7.9.1 (#4475)

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Amaury Levé <amauryleve@microsoft.com>

Directory.Packages.props

@@ -46,7 +46,7 @@
     <PackageVersion Include="Microsoft.TestPlatform.ObjectModel" Version="$(MicrosoftNETTestSdkVersion)" />
     <PackageVersion Include="Microsoft.TestPlatform.TranslationLayer" Version="$(MicrosoftNETTestSdkVersion)" />
     <PackageVersion Include="Microsoft.WindowsAppSDK" Version="1.0.0" />
-    <PackageVersion Include="Polyfill" Version="7.5.0" />
+    <PackageVersion Include="Polyfill" Version="7.9.1" />
     <PackageVersion Include="System.Threading.Tasks.Extensions" Version="$(SystemThreadingTasksExtensionsVersion)" />
     <!-- CVE-2019-0820 -->
     <PackageVersion Include="System.Diagnostics.TextWriterTraceListener" Version="4.3.0" />