Remove comment in security.rst about MySQL with PHP <= 5.3.6

docs/en/reference/security.rst

@@ -154,21 +154,4 @@ the ``Connection#quote`` method:
     $sql = "SELECT * FROM users WHERE name = " . $connection->quote($_GET['username'], \PDO::PARAM_STR);
 
 This method is only available for SQL, not for DQL. For DQL it is always encouraged to use prepared
-statements not only for security, but also for caching reasons.
-
-Non-ASCII compatible Charsets in MySQL
---------------------------------------
-
-Up until PHP 5.3.6 PDO has a security problem when using non ascii compatible charsets. Even if specifying
-the charset using "SET NAMES", emulated prepared statements and ``PDO#quote`` could not reliably escape
-values, opening up to potential SQL injections. If you are running PHP 5.3.6 you can solve this issue
-by passing the driver option "charset" to Doctrine PDO MySQL driver. Using SET NAMES does not suffice!
-
-.. code-block::
-
-    <?php    
-    $conn = DriverManager::getConnection(array(
-        'driver' => 'pdo_mysql',
-        'charset' => 'UTF8',
-    ));
-
+statements not only for security, but also for caching reasons.
\ No newline at end of file