[ticket/13892] Respect "Someone reports a post" notification setting.

report_post inherits from post_in_queue, therefore using self:: instead of
static:: results in the incorrect notification type being used to determine
which users to exclude from the notification.

PHPBB3-13892

phpBB/phpbb/notification/type/post_in_queue.php

@@ -108,7 +108,7 @@ class post_in_queue extends \phpbb\notification\type\post
 		}
 
 		return $this->check_user_notification_options($auth_read[$post['forum_id']]['f_read'], array_merge($options, array(
-			'item_type'		=> self::$notification_option['id'],
+			'item_type'		=> static::$notification_option['id'],
 		)));
 	}