Fix SoG pipeline by triggering off ADVOK label
This MR switches the trigger of the speed of gravity pipeline to use the ADVOK
label instead of GCN_PRELIM_SENT
in order to ensure the candidate is human-vetted (a candidate with GCN_PRELIM_SENT
and later with ADVNO
would not be suitable for SoG
analysis).
This MR also simplifies the workflow to trigger off of a superevent instead of an external event, reducing a step where GCN_PRELIM_SENT
needed to be applied to the external event.