Bump Polyfill from 7.5.0 to 7.6.0 in /src (#648)

Author: dependabot[bot]

src/Directory.Packages.props

@@ -8,7 +8,7 @@
     <PackageVersion Include="Microsoft.NET.Test.Sdk" Version="17.12.0" />
     <PackageVersion Include="NUnit" Version="4.2.2" />
     <PackageVersion Include="NUnit3TestAdapter" Version="4.6.0" />
-    <PackageVersion Include="Polyfill" Version="7.5.0" />
+    <PackageVersion Include="Polyfill" Version="7.6.0" />
     <PackageVersion Include="ProjectDefaults" Version="1.0.147" />
     <PackageVersion Include="Shipwreck.Phash.Bitmaps" Version="0.5.0" />
     <PackageVersion Include="System.Drawing.Common" Version="9.0.0" />