code: func (s *PullRequestsService) RemoveReviewers(ctx context.Context, owner, repo string, number int, reviewers ReviewersRequest) (*Response, error) {
  	u := fmt.Sprintf("repos/%s/%s/pulls/%d/requested_reviewers", owner, repo, number)
  	req, err := s.client.NewRequest("DELETE", u, &reviewers)
  	if err != nil {
  		return nil, err
  	}
  
  	return s.client.Do(ctx, req, nil)
  }
docs: // RemoveReviewers removes the review request for the provided reviewers for the specified pull request.
  //
  // GitHub API docs: https://developer.github.com/v3/pulls/review_requests/#delete-a-review-request