Change Antag Critter Spawns

[Kamikaze Mongoose]

I've noticed a very consistent pattern of very few critters being spawned during high pop on Main. It seems odd that 1 gunbot would spawn on a round with a 100+ population, let alone one that's 60+. I suspect they're weighted the same as full on antags which is odd since they're very watered down by comparison. It would be excellent if it would spawn slightly more critters with overall population taken into account similar to how it scales Nukies.

Main deserves more cleanbots, this is an outrage!