Singlehtml build throwing 'node not found' error

[AakashGC]

Describe the problem

When running jb build docs --builder pdfhtml on jupyter-book repo:

Exception occurred:
  File "/opt/hostedtoolcache/Python/3.8.12/x64/lib/python3.8/site-packages/sphinx/writers/html5.py", line 795, in unknown_visit
    raise NotImplementedError('Unknown node: ' + node.__class__.__name__)
NotImplementedError: Unknown node: HiddenCellNode

Discovered in this CI run: https://github.com/executablebooks/jupyter-book/pull/1499/checks?check_run_id=3865278435

Link to your repository or website

No response

Steps to reproduce

1. cd to jupyter-book repo location
2. Run jb build docs --builder pdfhtml

The version of Python you're using

No response

Your operating system

No response

Versions of your packages

sphinx-proof - v0.1.1
jupyter-book - v0.11.3

Additional context

No response