Use Python 3.10 on CI, at least for Jupyter Notebooks

[amotl]

About

Because we are aiming to run a signifcant portion of the assets here on Google Colab, most notably the Jupyter Notebooks, we may want to follow their cadence of Python updates.

Currently, Google Colab still seems to be on Python 3.10 ¹, so we may want to adjust the corresponding CI jobs to validate just that, in order to avoid any surprises.

/cc @marijaselakovic, @surister, @ckurze

Footnotes

1. https://colab.google/articles/py3.10 ↩

[amotl]

This patch will improve the situation.

• CI: Test Jupyter Notebooks also on Python 3.10 #425