Drop Python pre-3.9 logic

[jakirkham]

There is some leftover logic for older Python versions (pre-3.9). As we require Python 3.9+, this logic can be dropped. Would be good to clean things up a bit

[jakirkham]

Here's one instance

cucim/python/cucim/src/cucim/_misc.py

Lines 8 to 11 in d4ec01e

	if hasattr(math, "prod"):
	prod = math.prod # available in Python 3.8+ only
	else:
	prod = numpy.prod

[jakirkham]

Also these constraints could be refreshed

cucim/dependencies.yaml

Lines 206 to 209 in d4ec01e

	- matrix:
	py: "3.8"
	packages:
	- python=3.8

cucim/dependencies.yaml

Lines 218 to 220 in d4ec01e

	- matrix:
	packages:
	- python>=3.8,<3.11

[jakirkham]

We may also want to rerun the notebooks. For example:

cucim/notebooks/Welcome.ipynb

Line 48 in d4ec01e

"version": "3.8.10"

[jakirkham]

Might be worth adding pyupgrade to pre-commit