Add missing license header

Author: lyrixx

Tests/Transport/Smtp/EsmtpTransportFactoryTest.php

@@ -1,5 +1,14 @@
 <?php
 
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
 namespace Symfony\Component\Mailer\Tests\Transport\Smtp;
 
 use Symfony\Component\Mailer\Test\TransportFactoryTestCase;