Switch to new bridge auth "Serge"

We need to move to a new bridge authority, because our old one hasn't been getting enough maintenance or attention, and now it's stopped sending bridge descriptors to bridgedb entirely.

I've asked George to set up a new bridge authority, and he has: https://metrics.torproject.org/rs.html#details/BA44A889E64B93FAA2B114E02C2A279A8555C533

We should put out new releases, pointing to the new bridge authority, so that bridges can update and resume being advertised.