Fix docs build

[awaelchli]

What does this PR do?

The docs build has been blocking PRs with this error:

/home/runner/work/pytorch-lightning/pytorch-lightning/docs/source-pytorch/notebooks/course_UvA-DL/07-deep-energy-based-generative-models.ipynb:871: ERROR: Content block expected for the "raw" directive; none found.

See jupyter/nbconvert#2092

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📚 Documentation preview 📚: https://pytorch-lightning--19241.org.readthedocs.build/en/19241/

cc @Borda @tchaton

[github-actions]

⚡ Required checks status: All passing 🟢

Groups summary

🟢 fabric: Docs

Check ID	Status
docs-make (fabric, doctest)	success	✅
docs-make (fabric, html)	success	✅

These checks are required after the changes to requirements/docs.txt.

🟢 pytorch_lightning: Docs

Check ID	Status
docs-make (pytorch, doctest)	success	✅
docs-make (pytorch, html)	success	✅

These checks are required after the changes to requirements/docs.txt.

🟢 lightning_app: Docs

Check ID	Status
docs-make (app, doctest)	success	✅
docs-make (app, html)	success	✅

These checks are required after the changes to requirements/docs.txt.

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Thank you for your contribution! 💜

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[Borda]

lest just skip it I will need to fix more of them later...

[awaelchli]

I don't understand what you are saying. Took me a while to figure out it was this dependency, so please let us unblock development.