OpenRC Truggy Center Diff Bearing Fix

This is a quick fix that enables to use different bearing size for the center diff for the open RC truggy. I had issues with metal diff sourced from HobbyKing with each varying in bearing diameter. So decided to remix it to support possible bearing that I have encountered

6701 ZZ 12x18x4
6800 ZZ 10x19x5
6801 ZZ 12x21x5

So the only change is the outer diameter of the bearing to support different bearing sizes.
0.2 mm clearance has been added for each diameter of the bearing for easy f