Opening idler door for the Prusa Mk3s & MMU2s

Tested now. Seems to work well. :D At some stage I'll tweak it a bit more to thicken up some of the walls.

The MMU idler door for the MMU2s is a nuisance to open, as the lever used to activate the sensor interacts with the extruder body. This mod uses a 8mm M3 screw and bolt to disengage the lever from the idler door.

To open the door, just unscrew the main idler tensioning bolt. Then just unscrew the lever screw while opening the door.