MAGETWO-93702: [2.3] User can place order when product changes status to Out of stock during checkout

Author: serhii-balko

dev/tests/integration/testsuite/Magento/Checkout/_files/cart_with_simple_product_and_custom_options.php

@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+declare(strict_types=1);
 
 use Magento\Catalog\Api\Data\ProductCustomOptionInterface;
 use Magento\Catalog\Api\ProductRepositoryInterface;