Install networkx when testing functorch (#81403)
networkx is a required testing dependency. We're working on getting rid
of the dependency though (because ultimately we don't want PyTorch to
take a dependency on it).
Test Plan:
- wait for the functorch test shard in pytorch CI
Pull Request resolved: https://github.com/pytorch/pytorch/pull/81403
Approved by: https://github.com/ezyang, https://github.com/malfet
