chore(python): require 3.9; drop eol 3.8

[Rotzbua]

[Rotzbua]

@florianfesti FYI

The test fails with python 3.13 because the created svg is different. Spaces are missing because python changed how they handle doc strings:

The compiler now strips common leading whitespace from every line in a docstring.

https://docs.python.org/3/whatsnew/3.13.html#other-language-changes

Inconspicuous change with interesting effects....