🐛 docs no longer building

[frank1010111]

Describe the bug
Readthedocs is dying during builds due to a "AttributeError: 'Module' object has no attribute 'doc'" presumably related to multiwellproductivity.

To Reproduce
Steps to reproduce the behavior:
This is part of the CI/CD pipeline. It happens on each change to master.

Expected behavior
It passed until this pull request: https://github.com/frank1010111/pywaterflood/pull/57/files. Nox runs still pass.

nox -s docs

builds on Linux

[frank1010111]

To reproduce locally, run

python -m pip install .[docs]
cd docs
python -m sphinx -T -E -b html -d _build/doctrees -D language=en . _build/html

[frank1010111]

Not so fast! Turns out we do need myst_nb. See executablebooks/MyST-NB#543 for the specific issue.