Remove dotnet-core feed from NuGet.config

Author: pranavkm

NuGet.config

@@ -3,7 +3,6 @@
   <packageSources>
     <clear />
     <add key="AspNetCore" value="https://dotnet.myget.org/F/aspnetcore-ci-dev/api/v3/index.json" />
-    <add key="dotNetCore" value="https://dotnet.myget.org/F/dotnet-core/api/v3/index.json" />
     <add key="AspNetCoreTools" value="https://dotnet.myget.org/F/aspnetcore-tools/api/v3/index.json" />
     <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
   </packageSources>