cmd/aedeploy: remove "preview" from suggested gcloud command
cmd/aedeploy: remove "preview" from suggested gcloud command

Change-Id: If00535ecce770549272b5266174321a1b9dd6d40

fuchsia-mirror/third_party-github.com-golang-appengine,golang/appengine,golang/appengine,fuchsia-mirror/third_party-github.com-golang-appengine