Revert "package source changed to active"

This reverts commit 0f1c89346e.

nuget.config

@@ -1,6 +1,6 @@
 <?xml version="1.0" encoding="utf-8"?>
 <configuration>
-  <activePackageSource>
+  <packageSources>
     <add key="nuget.org" value="https://api.nuget.org/v3/index.json"/>
-  </activePackageSource>
+  </packageSources>
 </configuration>