fix for removed nuget feed

Author: asadsahi

NuGet.config

@@ -3,7 +3,6 @@
   <packageSources>
     <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
     <add key="aspnet-contrib" value="https://www.myget.org/F/aspnet-contrib/api/v3/index.json" />
-    <add key="aspnet-contrib-auth" value="https://www.myget.org/F/aspnetcore-authentication/api/v3/index.json" />
     <add key="AspNetCore" value="https://dotnet.myget.org/F/aspnetcore-ci-dev/api/v3/index.json" />
   </packageSources>
-</configuration>
+</configuration>