Use semantic tokens in app/assets/stylesheets/components/related_items_list.scss

See scan results at https://gitlab-org.gitlab.io/frontend/playground/gitlab-code-scanner/?search=check_id%20co%20%22color%22 for app/assets/stylesheets/components/related_items_list.scss

‎app/assets/stylesheets/components/related_items_list.scss#L42‎

background-color: $white;

‎app/assets/stylesheets/components/related_items_list.scss#L43‎

border-color: $gray-50;

‎app/assets/stylesheets/components/related_items_list.scss#L47‎

color: $red-500;

‎app/assets/stylesheets/components/related_items_list.scss#L64‎

color: $orange-500;

app/assets/stylesheets/components/related_items_list.scss#L72‎

color: $gray-900;