Update dependencies: downgrade Microsoft.Bcl.AsyncInterfaces to 6.0.0 and upgrade Polyfill to 8.7.4

Author: thomhurst

EnumerableAsyncProcessor/EnumerableAsyncProcessor.csproj

@@ -22,8 +22,7 @@
     </PropertyGroup>
 
     <ItemGroup Condition="'$(TargetFrameworkIdentifier)'!='.NETCoreApp'">
-        <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="9.0.3" />
-
+        <PackageReference Include="Microsoft.Bcl.AsyncInterfaces" Version="6.0.0" />
     </ItemGroup>
 
     <ItemGroup>
@@ -35,7 +34,7 @@
 
         <PackageReference Include="Microsoft.SourceLink.GitHub" Version="8.0.0" PrivateAssets="All"/>
 
-        <PackageReference Include="Polyfill" Version="7.26.0">
+        <PackageReference Include="Polyfill" Version="8.7.4">
           <PrivateAssets>all</PrivateAssets>
           <IncludeAssets>runtime; build; native; contentfiles; analyzers; buildtransitive</IncludeAssets>
         </PackageReference>