Update to current Python version

[jl-wynen]

ATTENTION when fixing this, check the current Python version!

The server and book currently use Python 3.11. But some notebooks still use old features, descriptions:

• 1-python/intermediate_topics.ipynb:
  • Type hints use List and Union. Update to new syntax.
• 1-python/sequence-data-types.ipynb:
  • dict is claimed to not have a specific order of elements. Either mention that elements are stored in insertion order or simply remove the sentence.

(The list is probably incomplete.)