use the latest python and jupyter-notebook releases

[PhiSpel]

    We could probably also update the docker image we use, currently we are using a legacy docker image running Python 3.6. The latest python release is 3.11. 

https://circleci.com/developer/images/image/cimg/python

Each tag contains a complete Python version via pyenv. pip, pipenv, and poetry are pre-installed [...]

I am not sure if the warning is relevant for us though, because it addresses uses by normal human beings, not by a CI script running in a container. I would have to check, but I think all commands are run as root anyway and the container is destroyed after the website has been built.

Originally posted by @joergbrech in #456 (comment)