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

Change-Id: If00535ecce770549272b5266174321a1b9dd6d40

cmd/aedeploy/aedeploy.go

@@ -36,7 +36,7 @@ var (
 
 func usage() {
 	fmt.Fprintf(os.Stderr, "Usage of %s:\n", os.Args[0])
-	fmt.Fprintf(os.Stderr, "\t%s gcloud --verbosity debug preview app deploy --version myversion ./app.yaml\tDeploy app to production\n", os.Args[0])
+	fmt.Fprintf(os.Stderr, "\t%s gcloud --verbosity debug app deploy --version myversion ./app.yaml\tDeploy app to production\n", os.Args[0])
 }
 
 func main() {