CON-47: fix params to select and fix SQL by using subquery

Please @sqlreview this SQL:

select distinct ug_user from user_groups where ug_group in ('sysop', 'bureaucrat') and ug_user not in (select distinct ug_user from user_groups where ug_group in ('bot', 'bot-global'))

Can it be written without subquery? Or optimized somehow?