Removes useless standard encryption keys from headsets

All radio headsets can use the common channel (;) independent of having any radio keys.

The fact that most of them start with useless 'standard' radio encryption keys (the default channel is unencrypted anyway??) is stupid, and makes departmental security annoying as well as transferring radio keys to different headsets.

Example: I'm engie sec, I want to put my departmental key into a bowman headset, but it has 2 keys already, so I have to take the keys out of my main headset, and then my bowman, and then transfer the two I want to the bowman, rather than just popping the two out of my standard headset and putting the engineering one into the bowman.

Also removes a bit of shitty code.

Fixes https://github.com/tgstation/-tg-station/issues/6475