Fixup feeds (#134)

Co-authored-by: Matt Mitchell <[email protected]>

Author: dotnet-bot

nuget.config

@@ -3,6 +3,6 @@
   <packageSources>
     <clear />
     <add key="dotnet-eng" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-eng/nuget/v3/index.json" />
-    <add key="nuget.org" value="https://api.nuget.org/v3/index.json" />
+    <add key="dotnet-public" value="https://pkgs.dev.azure.com/dnceng/public/_packaging/dotnet-public/nuget/v3/index.json" />
   </packageSources>
 </configuration>