R.I.P Assistant Antag Status

discussed on coderbus, majority seemed to agree assistants shouldn't be able to roll on station antag status.

it's supposed to be "Hi I don't know what I'm doing can you show me the ropes?"
Not MLG420QUICKCHOKEGREYTIDE

all in separate commits for cherrypicking the commits

this is a bugfix for our community picking assistant 24/7 because they seem to think assistant = first dibs on antag selection