Update trimesh/voxel.py
Update trimesh/voxel.py

Co-Authored-By: wkentaro <6cfe50a56e50adde2f7b87bae13362e897c28312@gmail.com>
dajusc/trimesh,mikedh/trimesh,mikedh/trimesh,dajusc/trimesh,mikedh/trimesh,mikedh/trimesh