MK4 buffer-frame-holder-reduced-hook_thickness

The MK4 "x-carriage-back" was able to hit the frame hook of this part so I adjusted its width.

After publishing this I found that a cable tie on the x-carriage cable outlet can interfere with this by about 1mm so I added “buffer-frame-holder-narrow-hook-trimmed-1mm.stl” and “Buffer Frame Holder_MK4 Frame R1_0.4n_0.2mm_PETG_MK4IS_15m.bgcode”

Chopped 2.2mm off the width of the hook to match the size of the MMU3 hooks.