Updated NuGet config file to resolve Microsoft.AspNetCore.App 2.1.3

NuGet.config

@@ -4,7 +4,7 @@
     <add key="repositoryPath" value="packages" />
   </config>
   <packageSources>
-    <add key="AspNetCore" value="https://dotnet.myget.org/F/aspnet-feb2017-patch/api/v3/index.json" />
+    <add key="AspNetCore" value="https://dotnet.myget.org/F/dotnet-core/api/v3/index.json" />
     <add key="NuGet" value="https://api.nuget.org/v3/index.json" />
   </packageSources>
 </configuration>