[master] Update dependencies from dotnet/corefx (dotnet/coreclr#23593)

- Microsoft.NETCore.Platforms - 3.0.0-preview4.19181.2
- Microsoft.Private.CoreFx.NETCoreApp - 4.6.0-preview4.19181.2


Commit migrated from https://github.com/dotnet/coreclr/commit/a437fc0091ee297061ebf4c134fe9b31e716d0cf

src/coreclr/tests/src/Common/test_dependencies/test_dependencies.csproj

@@ -25,6 +25,9 @@
     <PackageReference Include="System.Drawing.Common">
       <Version>$(MicrosoftPrivateCoreFxNETCoreAppVersion)</Version>
     </PackageReference>
+    <PackageReference Include="System.Runtime.Intrinsics.Experimental">
+      <Version>$(MicrosoftPrivateCoreFxNETCoreAppVersion)</Version>
+    </PackageReference>
   </ItemGroup>
   <PropertyGroup>
     <TargetFramework>netcoreapp3.0</TargetFramework>