fix (docs): remove warning for storage bucket existence.

Before 0.9.0 it was not possible to create a bucket using the library,
so it had to be done by other means.
Starting from 0.9.0 it is possible, so we can remove this warning.

lib/index.js

@@ -175,12 +175,6 @@ gcloud.pubsub = function(config) {
  * [Google Cloud Storage API docs]{@link https://developers.google.com/storage/}
  * for more information.
  *
- * You need to create a Google Cloud Storage bucket to use this client
- * library.
- * Follow the steps on
- * [Google Cloud Storage docs]{@link https://developers.google.com/storage/}
- * to create a bucket.
-
  * @type {module:storage}
  *
  * @return {module:storage}