message: docs: update site link for UpdateTopicRequest
  The old link wasn't valid anymore, I'm guessing due to an update to the docs site.
diff: @@ -834,7 +834,7 @@ export class Topic {
  /**
  * Updates the topic.
  *
  - * @see [UpdateTopicRequest API Documentation]{@link https://cloud.google.com/pubsub/docs/reference/rest/v1/UpdateTopicRequest}
  + * @see [UpdateTopicRequest API Documentation]{@link https://cloud.google.com/pubsub/docs/reference/rpc/google.pubsub.v1#google.pubsub.v1.UpdateTopicRequest}
  *
  * @param {object} metadata The fields to update. This should be structured
  * like a {@link
  