code: func (s *ChangesService) DeleteTopic(changeID string) (*Response, error) {
  	u := fmt.Sprintf("changes/%s/topic", changeID)
  	return s.client.DeleteRequest(u, nil)
  }
docs: // DeleteTopic deletes the topic of a change.
  // The request body does not need to include a TopicInput entity if no review comment is added.
  //
  // Please note that some proxies prohibit request bodies for DELETE requests.
  // In this case, if you want to specify a commit message, use PUT to delete the topic.
  //
  // Gerrit API docs: https://gerrit-review.googlesource.com/Documentation/rest-api-changes.html#delete-topic