addRemoveLabel = async (octokit, prNumber, owner, repo, label, add) => {
  const res = await octokit.rest.pulls.get({
    owner,
    repo,
    pull_number: prNumber,
  });
  if (add) {
    if (!res.data.labels.find((l) => l.name === label)) {
      await addLabel(octokit, prNumber, owner, repo, [label]);
    }
  } else {
    if (res.data.labels.find((l) => l.name === label)) {
      await removeLabel(octokit, prNumber, owner, repo, label);
    }
  }
}
Adds or removes a label from the pull request.

@param {Object} octokit Octokit instance.
@param {number} prNumber Pull request number.
@param {string} owner Repository owner.
@param {string} repo Repository name.
@param {string} label Label to add or remove.
@param {boolean} add Whether to add or remove the label.
@returns {Promise<void>} Promise.