Expose signoff box for RRT Level 0 responders
Make the signoff box (ADVOK/ADVNO) on GraceDB ADVREQ events available to RRT Level 0 responders, i.e. those who belong to Services:GraceDB:PrivilegedGroups:RRT:authorized
(LV) or gw-astronomy:KAGRA-LIGO:graceDB:privilegedGroups:RRT
(KAGRA).
Without this, RRT cannot send Initial or Retraction Notice and Circular.
I don't think Level 0 responders should have access to "Exposing/hiding superevents" button, though.