Fix linting error: add required newline at end of file

- Add missing newline at end of list-sales-order-items.mjs
- Resolves 'Newline required at end of file but not found' lint error

Author: seynadio

components/returnless/actions/list-sales-order-items/list-sales-order-items.mjs

@@ -36,4 +36,4 @@ export default {
       : "s"} from order ${this.orderId}`);
     return salesOrderItems;
   },
-};
+};