Remove code for EOL Python versions #1185

Job	Run time
Run tests with coverage	3m 9s
Run tests (3.8)	2m 10s
Run linters (flake8)	1m 44s
Run tests (3.9)	2m 5s
Run linters (pydocstyle)	1m 46s
Run tests (3.10)	2m 4s
Run tests on legacy versions (3.7)	2m 14s
Run linters (mypy)	1m 49s
Run tests with different pydantic versions	3m 45s
Run tests (3.11)	2m 9s
Run linters (pylint)	1m 56s
Run tests (3.12)	2m 11s
Run tests (3.13)	2m 15s
	29m 17s

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