Fix chicken-egg notebook versioning issue

[atmorling]

Currently when cutting a new release, one has to update the version tag in the notebooks to the tag that doesn't exist yet, in order for the docs build of the release to refer to the correct version.

This causes an issue if done via a PR in that the notebook tests will fail, and committing to main isn't ideal.

Options I can think of:

• Add a label to optionally skip notebook tests for a pre-release PR
• Have elebot generate the PR based on a workflow_dispatch and skip the notebook tests in this case
• Move the docs / notebook build out of this repo entirely (probably more effort than necessary for now)