Remove obsolete PubSub references from docs #1789
Description
https://github.com/GoogleCloudPlatform/google-cloud-java/blob/master/TESTING.md
https://github.com/GoogleCloudPlatform/google-cloud-java/blob/master/README.md
grep for any others too.