[ticket/17414] Clean up small code issues noticed by sniffer

PHPBB-17414

phpBB/phpbb/captcha/plugins/base.php

@@ -1,4 +1,15 @@
 <?php
+/**
+ *
+ * This file is part of the phpBB Forum Software package.
+ *
+ * @copyright (c) phpBB Limited <https://www.phpbb.com>
+ * @license GNU General Public License, version 2 (GPL-2.0)
+ *
+ * For full copyright and license information, please see
+ * the docs/CREDITS.txt file.
+ *
+ */
 
 namespace phpbb\captcha\plugins;