code: public CompletableFuture<Void> deleteRuleAsync(String topicPath, String subscriptionName, String ruleName) {
          EntityNameHelper.checkValidTopicName(topicPath);
          EntityNameHelper.checkValidSubscriptionName(subscriptionName);
          EntityNameHelper.checkValidRuleName(ruleName);
          String path = EntityNameHelper.formatRulePath(topicPath, subscriptionName, ruleName);
          return deleteEntityAsync(path);
      }
docs: Deletes the rule for a given topic-subscription.
  @param topicPath - The name of the topic.
  @param subscriptionName - The name of the subscription.
  @param ruleName - The name of the rule.
  @return A completable future that completes when the rule is deleted.
  @throws IllegalArgumentException - path is not null / empty / too long / invalid.