possibly fixes getting the same antagonist type twice
Created by: Intigracy
I suspect that byond's remove() proc is slower than just doing list -= var.
This for sure won't fix getting both traitor and changeling, but I believe it will fix getting traitor 2-3 times at once.
All I've done here is taken the two antagonists this is known to happen with (traitor and changeling) and made the code match all the other game mode pre-setups when assigning antags.
maybe fixes #10948 (closed)