You'll need to do 4 things:
- Refresh your keyring
pacman-keyring --init
pacman-keyring --populate archlinux
- Remove the archlabs section from your pacman.conf
pacman -Syyu
- Maintenance: https://wiki.archlinux.org/title/System_maintenance#Check_for_orphans_and_dropped_packages
This should be everything. You'll need to be careful with removing packages with no upstream. I'm not sure how archlabs distributed their configuration files but if they were packages you'll have to be selective about what you remove. Ideally you'll slowly drop those configs for your own versions with future upgrades.