message: Deemphasize `update-pr-from-base-branch` button
diff: /* Hide extra copy on PR mergeability summary */
  .mergeability-details .js-details-container .h4,
  -.mergeability-details .js-details-container .status-meta .btn-link,
  -.mergeability-details > :not(.js-details-container) .completeness-indicator-success ~ .status-meta { /* Hides merge information unless it's negative */
  +.mergeability-details .js-details-container .status-meta:not(.rgh-update-pr-from-base-branch) .btn-link,
  +.mergeability-details > :not(.js-details-container) .completeness-indicator-success ~ .status-meta:not(.rgh-update-pr-from-base-branch) { /* Hides merge information unless it's negative */
  display: none;
  }
  