Upgrade Jupyter Notebook files to use 4.5 format

[MSeal]

In testing some reported issues in papermill, I noticed that the VS Code python extension was still outputting version 4.2 notebooks. The current spec is at 4.5 and given the popularity of VSCode for notebook development I think it'd help with tooling and maintenance if specs were caught up to current versions. The spec for older 4.x formats was back-ported to account for some 4.4 features being saved in older versions, but I'd still recommend at a minimum moving to 4.4 and plan / update to 4.5's addition of cell_id.

Happy to help discuss any concerns or details around the spec / upgrade.

[joyceerhl]

Appreciate you bringing this to our attention @MSeal, we'll discuss prioritization for migrating to 4.4/4.5 at our team's weekly triage 😊 Thank you!

[joyceerhl]

@MSeal It seems like JupyterLab itself doesn't support 4.5 yet. Would upgrading, either to 4.4 or 4.5, cause compatibility issues for our users who then open a 4.4/4.5 notebook in older versions of Jupyter?