simplified whistle

Internally a direct copy of [this whistle](https://www.thingiverse.com/thing:2933021) but an easier and slightly faster print. Optimized for 0.8mm nozzle with 1 wall and no infill. Performs the same or slightly louder.

There are probably louder whistles on here but I wouldn't recommend using them without ear protection. This one is already pushing the limits.