Changed the URLs for google repository.
Changed the URLs for google repository.

Reviewed in https://codereview.appspot.com/97160043/

elharo/appengine-maven-archetypes-java,GoogleCloudPlatform/appengine-maven-archetypes-java,GoogleCloudPlatform/appengine-maven-archetypes-java,elharo/appengine-maven-archetypes-java,GoogleCloudPlatform/appengine-maven-archetypes-java,GoogleCloudPlatform/appengine-maven-archetypes-java,elharo/appengine-maven-archetypes-java,elharo/appengine-maven-archetypes-java