fix(docs): move to new client docs URL (#733)

Author: Benjamin E. Coe

.repo-metadata.json

@@ -2,9 +2,9 @@
  "name": "google-auth-library",
  "name_pretty": "Google Auth Library",
  "product_documentation": "https://cloud.google.com/docs/authentication/",
- "client_documentation": "https://googleapis.dev/nodejs/google-auth-library/latest/",
+ "client_documentation": "https://googleapis.dev/nodejs/google-auth-library/latest",
  "release_level": "ga",
  "language": "nodejs",
  "repo": "googleapis/google-auth-library-nodejs",
  "distribution_name": "google-auth-library"
-}
+}