There's a merged pull request on the void-packages repository

python3-networkx: update to 2.4 and remove python-networkx
https://github.com/void-linux/void-packages/pull/14558

Description:
Python 2.x is no longer supported:

https://networkx.github.io/documentation/stable/release/release_2.3.html

Python 3.x is still supported (python3-networkx).