MAINT: drop Python 3.7 & 3.8 support due to EOL #506

Job	Run time
pytest / Determine job matrix	6s
style / Determine skipped pre-commit hooks	10s
doc / nb / Execute and build documentation	46s
doc / linkcheck / Check external links	39s
pytest / Run unit tests (3.10, ubuntu-24.04)	1m 20s
pytest / Run unit tests (3.11, ubuntu-24.04)	1m 11s
pytest / Run unit tests (3.12, ubuntu-24.04)	1m 11s
pytest / Run unit tests (3.9, ubuntu-24.04, qrules)	4m 19s
pytest / Run unit tests (3.9, macos-14)	1m 9s
style / Run local pre-commit hooks	45s
style / Run taplo through pre-commit	0s
doc / Upload to GitHub Pages	0s
style / Push changes	0s
	11m 36s

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