message: Fix alignment of the "Update branch" button for PRs
diff: .mergeability-details .branch-action-item-icon {
  margin-top: -4px;
  }
  -.mergeability-details .branch-action-item .float-right.btn {
  +.mergeability-details .branch-action-item .btn {
  margin-top: -6px;
  }
  .alt-merge-options {
  