Make sure the `random.Generator` interface is used in all tutorials

[rossbar]

The tutorials should use the recommended random.Generator interface for random number generation. A quick grep shows that there are some instances of the older usage in the following files:

• tutorial-nlp-from-scratch.md
• text_preprocessing.py

It would be a nice improvement to replace these instances with the recommended random interface.

[willhoh]

May I work on that? I used numpy in some tutorials and only in vs-code on simple python files. However, I would like to take on this task to maybe get an introduction to Jupiter Notebooks, but especially to learn how to contribute to open-source software.

[Mukulikaa]

@willhoh, NumPy doesn't assign issues so go ahead! Feel free to ping if you need any help.