Using timelimit command in-game writes an oddly specific time to game-options.json

The /bingo timelimit command is implemented so that running /bingo timelimit 30 will always result in exactly 30 minutes remaining, regardless of how much game time has already elapsed. However, the game duration still reflects the total time spent in the game.

This has a side-effect of writing a very specific time limit to the game options, which then gets reused for the next round.

The game should discard the time limit adjustment after the game so that 30 minutes is the time limit that persists.