CI is failing creating html from notebooks

[woodsp-ibm]

Nightly CI has been failing for the past 3 days (the contents of the repo have not changed at all in that time).

/home/runner/work/qiskit-machine-learning/qiskit-machine-learning/docs/tutorials/05_torch_connector.ipynb:1959: ERROR: Content block expected for the "raw" directive; none found.

... repeated many times

One change that I do notice is that nbconvert is now 7.14.0, and has been failing since that version, where the last time it passed was when 7.13.1 was the latest.

See also qiskit-community/qiskit-algorithms#117 which links to what seems a similar issue raised on nbconvert