Removes audio play

[alexmgriffiths]

Addresses #288

Commit f1cb51a introduced the following code which breaks since game.audio is undefined.

  if (!code.hasClass('correct')) {
    game.audio.correct.play();
  }

This removes the above block.

I removed it because I didn't see an audio file or any other reference for game.audio so I'm assuming it is a feature still in development that got merged early.