[MIRROR] Removes the old toolbox arena code (#1191)

* Removes the old toolbox arena code (#81707)

## About The Pull Request

This machine was added 5 years ago to be used for events like the
toolbox tournament, but it has since been deprecated and unused (toolbox
tournament has made their own version of the console that works much
better and uses TGUI), making this machine not worth touching.
After some discussions in discord, we said the better option would be to
remove this machine and leave the toolbox tournament branch keep using
their machine, rather than to port the toolbox version to TG where it
will continue to not be used in-game.

fun fact: This used to have a feature where it gave antag hud icons to
the members of each team, it was removed when antag huds got refactored
3 years ago, hence why I'm removing an antag hud icon.

## Why It's Good For The Game

Already explained, this machine has no purpose as it is now, and a new
tgui UI won't save it.

## Changelog

Nothing player-facing.

* Removes the old toolbox arena code

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Co-authored-by: John Willard <[email protected]>