Fix fairchem and neighbors tests

[WillEngler]

Summary

We were seeing failures in CI like this:

/home/runner/work/_temp/cac890cb-6b9c-4ccf-b501-261afaef31a8.sh: line 3: huggingface-cli: command not found

It seems this is because Hugging Face changed the name of their CLI from huggingface-cli to hf. (details here) This PR updates our test setup to reflect this.

We were also seeing test failures in CI in test_neighbors.py that looked like this:

FAILED tests/test_neighbors.py::test_neighbor_list_implementations[vesin_nl-periodic_atoms_set-1] - ValueError: `periodic` must be a single boolean or a sequence of three booleans, got True of type <class 'numpy.ndarray'>

The proximate cause of this failure seems to be that vesin recently bumped to 0.4.0 (link). Their release notes mention that ...

The periodic argument to vesin_neighbors() in C and C++, NeighborList.compute() in all other languages can now be set separatly for each box dimension, allowing mixed periodic and non-periodic boundary conditions.

I cut this issue to properly handle this change, but in the meantime I enforced vesin < 0.4.0 in pyproject.toml.

Checklist

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• Doc strings have been added in the Google docstring format.
• Run ruff on your code.
• Tests have been added for any new functionality or bug fixes.

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