Remove gang from rotation entirely

[DJ-Fireball_did_this]

I think, judging from other servers, gang could actually have potential to be highly destructive and engaging. Lots of servers do this sort of "cross-fire" thing where two groups of antags are trying to destroy eachother and the crew is caught in the middle. If gang was more focused on that it would be far more entertaining. Goon also doesn't have any antags like that besides kinda rev and I think it's a niche worth looking into.