message: Shrink text field after `clear-pr-merge-commit-message`
diff: import React from 'dom-chef';
  import select from 'select-dom';
  +import {set} from 'text-field-edit';
  import * as pageDetect from 'github-url-detection';
  import features from '../feature-manager';
  @@ -31,7 +32,7 @@ async function init(): Promise<void | false> {
  return false;
  }
  - messageField.value = cleanedMessage;
  + set(messageField, cleanedMessage);
  messageField.after(
  <p className="note">
  The description field was cleared by <a target="_blank" href="https://github.com/refined-github/refined-github/wiki/Extended-feature-descriptions#clear-pr-merge-commit-message" rel="noreferrer">Refined GitHub</a>.
  