tests/data/zoneinfo_data.json contains outdated tzdata 2022g

[robert-scheck]

While trying to work around #124, I had to learn that tests/data/zoneinfo_data.json in Git is currently outdated as it only ships tzdata 2022g, while even an LTS distribution such as Red Hat Enterprise Linux 8 / Rocky Linux 8 ship tzdata 2023c (leading to a test failure due to differences in the actual test data).

Unfortunately, scripts/update_test_data.py depends on the zoneinfo module which leads (at least for me) to a "chicken or the egg" dilemma.