strict type declaration inside async api functional test

Author: Vasiliev.A

dev/tests/api-functional/testsuite/Magento/WebapiAsync/Model/AsyncBulkScheduleTest.php

@@ -4,6 +4,8 @@
  * See COPYING.txt for license details.
  */
 
+declare(strict_types=1);
+
 namespace Magento\WebapiAsync\Model;
 
 use Magento\Catalog\Api\Data\ProductInterface;