Demo script segfaults on visualize

[elchun]

Steps to reproduce:

Make fresh install without using contact_graspnet_env.yml, then run:

python contact_graspnet_pytorch/inference.py \
       --np_path="test_data/*.npy" \
       --local_regions --filter_grasps

Then system segfaults after Visualizing... is printed.

[elchun]

This appears to be an issue with the paint_uniform_color function in open3d. According to this issue, the current solution is to downgrade from numpy 2.0 to a 1.* version. This was verified to fix the issue.