Notebook pre-processing failing

[mattwthompson]

From a cursory look, PyArrow is treated as an optional dependency but also needing for one of the NAGL notebooks

https://github.com/openforcefield/openff-docs/actions/workflows/cookbook_preproc.yaml

[j-wags]

Marked as urgent in zenhub

[mattwthompson]

@Yoshanuikabundi handled this in #94