Handle end of support of Python 3.8

End of support of 3.8 is planned for October 2024 cf. https://peps.python.org/pep-0569/

Minimal version of S1Tiling must move to 3.9 before this date to avoid issue.

Moreover it could be interesting to check the new features offered by this version cf. https://docs.python.org/3/whatsnew/3.9.html and identify the ones which can be used in S1Tiling.