Pointed to a version of MW CheckUser extension that works with a new wiki install

Pointed to a version of MW CheckUser extension that works with a new wiki install

Fixes CheckUser failure logged at https://travis-ci.org/openstreetmap/chef/jobs/650204578

    Wikimedia\Rdbms\DBQueryError from line 1587 of /srv/wiki.openstreetmap.org/w/includes/libs/rdbms/database/Database.php: A database query error has occurred. Did you forget to run your application's database schema updater after upgrading?
    Query: INSERT  INTO `cu_changes` (cuc_timestamp,cuc_user,cuc_user_text,cuc_namespace,cuc_title,cuc_comment,cuc_minor,cuc_page_id,cuc_this_oldid,cuc_last_oldid,cuc_type,cuc_ip,cuc_ip_hex) VALUES ('20200203011622',NULL,'MediaWiki default','0','Main_Page','','0','1','1','0','1','127.0.0.1','7F000001')
    Function: PopulateCheckUserTable::doDBUpdates
    Error: 1048 Column 'cuc_user' cannot be null (localhost)
    Backtrace:
    #0 /srv/wiki.openstreetmap.org/w/includes/libs/rdbms/database/Database.php(1556): Wikimedia\Rdbms\Database->getQueryExceptionAndLog(string, integer, string, string)
    #1 /srv/wiki.openstreetmap.org/w/includes/libs/rdbms/database/Database.php(1274): Wikimedia\Rdbms\Database->reportQueryError(string, integer, string, string, boolean)
    #2 /srv/wiki.openstreetmap.org/w/includes/libs/rdbms/database/Database.php(2149): Wikimedia\Rdbms\Database->query(string, string)
    #3 /srv/wiki.openstreetmap.org/w/extensions/CheckUser/maintenance/populateCheckUserTable.php(98): Wikimedia\Rdbms\Database->insert(string, array, string)
    #4 /srv/wiki.openstreetmap.org/w/maintenance/Maintenance.php(1719): PopulateCheckUserTable->doDBUpdates()
    #5 /srv/wiki.openstreetmap.org/w/maintenance/update.php(215): LoggedUpdateMaintenance->execute()
    #6 /srv/wiki.openstreetmap.org/w/maintenance/doMaintenance.php(96): UpdateMediaWiki->execute()
    #7 /srv/wiki.openstreetmap.org/w/maintenance/update.php(275): require_once(string)
    #8 {main}