Drop Python 3.9 support

[martinholmer]

The following line 6 does not work under Python 3.9 because the | notation for Union was introduced into Python typing beginning with Python 3.10.

policyengine-core/policyengine_core/types/data_types/arrays.py

Lines 1 to 6 in 47f5bdf

	from typing import Sequence, TypeVar, Any
	from numpy.typing import NDArray as ArrayType
	T = TypeVar("T", bool, bytes, float, int, object, str)
	ArrayLike = ArrayType[Any] | Sequence[T]

I suggest revising setup.py to require Python 3.10, 3.11, or 3.12.

[anth-volk]

Closed as part of #286.