WP_DEBUG error with register_uninstall_hook

If you turn on WP_DEBUG, you’ll get

Notice: register_uninstall_hook was called <strong>incorrectly</strong>. Only a static class method or function can be used in an uninstall hook. Please see <a href="https://codex.www.ads-software.com/Debugging_in_WordPress">Debugging in WordPress</a> for more information. (This message was added in version 3.1.) in /var/www/wp-includes/functions.php on line 2758

based on line 55 : register_uninstall_hook(__FILE__, array(&$this, 'deactivate'));

https://www.ads-software.com/extend/plugins/update-notifications-manager/