fix(docs): move to new client docs URL (#368)

Author: bcoe

packages/google-cloud-dialogflow/.repo-metadata.json

@@ -2,12 +2,12 @@
   "name": "dialogflow",
   "name_pretty": "Dialogflow API",
   "product_documentation": "https://cloud.google.com/dialogflow-enterprise/",
-  "client_documentation": "https://cloud.google.com/dialogflow-enterprise/docs/reference/rpc/",
+  "client_documentation": "https://googleapis.dev/nodejs/dialogflow/latest",
   "issue_tracker": "https://issuetracker.google.com/savedsearches/5300385",
   "release_level": "beta",
   "language": "nodejs",
   "repo": "googleapis/nodejs-dialogflow",
   "distribution_name": "dialogflow",
   "api_id": "dialogflow.googleapis.com",
   "requires_billing": true
-}
+}