message: docs: Update documentation for Subscription
diff: @@ -169,7 +169,7 @@ export interface SubscriptionMetadata extends TSubscriptionMetadata {
  * // message.ackId = ID used to acknowledge the message receival.
  * // message.data = Contents of the message.
  * // message.attributes = Attributes of the message.
  - * // message.timestamp = Timestamp when Pub/Sub received the message.
  + * // message.publishTime = Timestamp when Pub/Sub received the message.
  *
  * // Ack the message:
  * // message.ack();
  