Use dotnet-core feed in repos

build/sources.props

@@ -1,10 +1,11 @@
-<Project>
+<Project>
   <Import Project="$(DotNetRestoreSourcePropsPath)" Condition="'$(DotNetRestoreSourcePropsPath)' != ''"/>
 
   <PropertyGroup Label="RestoreSources">
     <RestoreSources>$(DotNetRestoreSources)</RestoreSources>
     <RestoreSources Condition="'$(DotNetBuildOffline)' != 'true' AND '$(AspNetUniverseBuildOffline)' != 'true' ">
       $(RestoreSources);
+      https://dotnet.myget.org/F/dotnet-core/api/v3/index.json;
       https://dotnet.myget.org/F/aspnetcore-dev/api/v3/index.json;
       https://dotnet.myget.org/F/aspnetcore-tools/api/v3/index.json;
     </RestoreSources>