Update gcloud versions (#361)

Update latest gcloud versions

Author: google-github-actions-bot

data/versions.json

@@ -494,5 +494,6 @@
   "536.0.1",
   "537.0.0",
   "538.0.0",
-  "539.0.0"
+  "539.0.0",
+  "540.0.0"
 ]