Update to the 12.4-RELEASE schedule

From: Glen Barber <gjb_at_freebsd.org>
Date: Thu, 17 Nov 2022 16:45:59 UTC
As it turns out, 12.4-RC3 is not needed during this release cycle.  As 
such, the next build will be 12.4-RELEASE, scheduled for November 30, in
order to avoid conflicts with the US Thanksgiving holiday.