Update nuget.config

Author: alerickson

nuget.config

@@ -2,8 +2,7 @@
 <configuration>
   <packageSources>
     <clear />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
-  </packageSources>
+    <add key="PowerShellCore_PublicPackages" value="https://pkgs.dev.azure.com/powershell/PowerShell/_packaging/powershell/nuget/v3/index.json" />  </packageSources>
   <disabledPackageSources>
     <clear />
   </disabledPackageSources>