Prusa PSU replacement frame brace

Remix of the frame brace used in _the_ [Prusa enclosure](https://www.youtube.com/watch?v=oS7ZtBNh2hE). Pretty simple, just thought it was a lot of plastic going to waste in the original one, so cut out the centre to try and reduce plastic usage.

Cut out as much as i thought i could and still have it solid. The part came out really strong, so could probably shave off a lot more on the insides and on the two panels that get bolted to the frame.

Also used 50% infill which was probably unnece