Update Connection.php

These events don't exist.

lib/Doctrine/DBAL/Connection.php

@@ -1251,9 +1251,6 @@ class Connection implements DriverConnection
     /**
      * Cancels any database changes done during the current transaction.
      *
-     * This method can be listened with onPreTransactionRollback and onTransactionRollback
-     * eventlistener methods.
-     *
      * @throws \Doctrine\DBAL\ConnectionException If the rollback operation failed.
      */
     public function rollBack()