How to remove a dead binary cache from config

Recently garnix shutdown, which mean trying to rebuild my config while having it as a subsituter just failswith a bad gateway. Issue is, to remove it from my config, i gotta rebuild my config, which obviously fails since it tries to check for garnix. Not sure what to do here

EDIT: I fixed by by "overriding" my nix config, I jsut copied the substituter related entry in the nix.conf geberated by nix, pasted them in ~/.config/nix/nix.conf and removed garnix from those, then just rebuild the config and boom it worked. Just dot forget to then remove those lines from the user nix config