gitlab-org--gitlab-foss/app/assets/stylesheets/components/milestone_combobox.scss

.milestone-combobox {
  .selected-item {
    /* stylelint-disable-next-line function-url-quotes */
    background: url(asset_path('checkmark.png')) no-repeat 0 2px;
  }

  .dropdown-item-space {
    padding: 8px 12px;
  }

  .dropdown-menu.show {
    overflow: hidden;
  }
}