Items held by slim player models are offset

Classic skins can be one of two models: Wide or Slim. Wide models feature 4 texel wide arms, and slim models feature 3 texel wide arms.

The right and left item holding pivots for wide skins is properly centered on the arm's X axis, but weren't modified in the slim model to accomodate the slimmer arms.

This can be fixed by changing their right and left item pivots' X positions respectively from -6.0 and 6.0 to -5.5 and 5.5.