[GAMEPLAY] /mute all logic is wrong

Steps to reproduce:

1. Hold tab to open the players interface and click the little speaker button next to Player A to mute them.
2. Type "/mute all" in the chat to mute all players in the game.
3. Player A has now somehow been unmuted and you can now see them chat.

The logic here is clearly wrong. It doesn't make sense at all for your code to flip the "isMuted" values when trying to "mute all"... you should just set them all to true.