Add exception to update joint FAR for neutrino events
There is a bug in the current implementation of the RAVEN pipeline that expects a joint FAR to be calculated to update these values in the superevent: https://git.ligo.org/emfollow/gwcelery/-/blob/732772c1d5a66a7810a7f53dbf2812cd1b763ab4/gwcelery/tasks/raven.py
This could be fixed by checking if the external event is a SNEWS (or more generally a neutrino burst event) and ignore updating the joint FAR: https://git.ligo.org/emfollow/gwcelery/-/blob/732772c1d5a66a7810a7f53dbf2812cd1b763ab4/gwcelery/tasks/raven.py#L238
This already similarly done with calculating the joint FAR: https://git.ligo.org/emfollow/gwcelery/-/blob/732772c1d5a66a7810a7f53dbf2812cd1b763ab4/gwcelery/tasks/raven.py#L35-36