[SFI] Avoid download from nuget.org directly in the Agg pipeline (#371)

* Update nuget.config

* Update nuget.config

Author: alexlamtest

Samples/nuget.config

@@ -9,7 +9,11 @@
     </packageRestore>
     <packageSources>
         <clear />
-        <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+        <!--
+            Resort to using this direct reference to nuget.org in case of no access to the internal feed below.
+            <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+        -->
+        <add key="ProjectReunion internal" value="https://microsoft.pkgs.visualstudio.com/ProjectReunion/_packaging/Project.Reunion.nuget.internal/nuget/v3/index.json" />
 
         <!-- a local directory to allow testing nupkg files without pushing to a remote feed -->
         <add key="localpackages" value="localpackages" />