Update LGCP notebook to v4

[fonnesbeck]

In addition to updating to v4, I removed the second model from the notebook. The first model already takes upward of an hour to run on a reasonably fast PC; the second model takes almost a day.

The notebook has also been moved from the case studies folder to the gaussian processes folder.

[review-notebook-app[bot]]

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[twiecki]

NB looks good, but pre-commit. Probably need to update myst file.

[OriolAbril]

There is a typo caught by codespell check: https://github.com/pymc-devs/pymc-examples/runs/6758385057?check_suite_focus=true#step:5:84. "accomodate" only has one m and is being updated to "accommodate"