Bump python to 3.12 for build docs workflows

[Czaki]

References and relevant issues

Description

Follow the main repo and change from Python 3.10 to python 3.12

[psobolewskiPhD]

If/when the action succeeds, mark ready-to-merge to kick off the full builds (circle and GH) and let that complete, just to ensure everything is gucci there too.

[TimMonko]

good change regardless, merge once all passes. thanks @Czaki

[psobolewskiPhD]

@napari-bot make docs

(this should execute the code cells in the docs but skip the other time consuming things, lets see if it also fails)

[psobolewskiPhD]

Here's the run: https://github.com/napari/docs/actions/runs/17986832367/job/51167065334
(not sure the status will be updated properly 😬 )

Edit: it failed in just 3 min, so big savings for troubleshooting efforts, and it did update the status.

[brisvag]

So we should get this in despite the red, and then work from there to fix CI?

[Czaki]

We should merge napari/napari#8307 and then check again.

[brisvag]

@napari-bot make docs

[brisvag]

Looks like we're good!