Fix cursor_demo wrt. Line2D.set_x/ydata not accepting scalars anymore.

[anntzer]

Trying to run the example prior to the PR would result in exceptions being thrown on mouse moves.

PR Summary

PR Checklist

Documentation and Tests

• Has pytest style unit tests (and pytest passes)
• Documentation is sphinx and numpydoc compliant (the docs should build without error).
• New plotting related features are documented with examples.

Release Notes

• New features are marked with a .. versionadded:: directive in the docstring and documented in doc/users/next_whats_new/
• API changes are marked with a .. versionchanged:: directive in the docstring and documented in doc/api/next_api_changes/
• Release notes conform with instructions in next_whats_new/README.rst or next_api_changes/README.rst

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout v3.7.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 f10d0d16a7ff0dc622f388dac5090029af2f017f

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #25106: Fix cursor_demo wrt. Line2D.set_x/ydata not accepting scalars anymore.'

4. Push to a named branch:

git push YOURFORK v3.7.x:auto-backport-of-pr-25106-on-v3.7.x

5. Create a PR against branch v3.7.x, I would have named this PR:

"Backport PR #25106 on branch v3.7.x (Fix cursor_demo wrt. Line2D.set_x/ydata not accepting scalars anymore.)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.

[ksunden]

Manual backport rolled into #25160