Delete RT permission that causes too many options at the "Owner" select on Ticket creation screen:

rt_permission_cleanup.sql

-- Delete any ACL allowing everyone to own ticlets for any queue
DELETE FROM ACL WHERE id IN (
   SELECT id FROM ACL WHERE RightName='OwnTicket' AND objecttype='RT::Queue' AND principalid IN (
      SELECT id FROM Groups WHERE domain='SystemInternal' AND type='Everyone'
   )
);