Wanhao i3 Z endstop - No extra bolts needed

Thought we needed an endstop bracket that doesn't depend on having to buy two M2 nuts and bolts.

This locates the switch by means of interference fit around the vertical walls of the switch body. It's a nice snug fit so be careful when removing if you have to.

Don't throw away the two bolts that originally mounted the switch as they're used to mount the bracket to the frame.