Removed DEALLOCATE in prepared statement destruct

    Prepared statements __destruct method was in charge of deallocating
    the statement in the database. While doing so, it used getHandler()
    from the connection to issue statements.
    But PreparedQuery instances are freed by the garbage collector when
    the Connection instance dies. This means the getHandler() call
    re-initiates a connection when there are too much statements to
    deallocate. This new connection does not know the prepared
    statements the instances try to deallocate resulting in error
    spawning in the logs.
    If killing a connection also drops the prepared statements issued,
    there is no need take the time to deallocate them one by one.