Add missing Copyright

Author: lbajsarowicz

dev/tests/api-functional/testsuite/Magento/ProductVideo/ProductVideoExternalSourceTest.php

@@ -1,4 +1,8 @@
 <?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
 declare(strict_types=1);
 
 namespace Magento\ProductVideo;