Remove Python 3.9 from wheels

[kylebarron]

[kylebarron]

Oops, I should've included this in #481 , but forgot.

We still allow Python 3.9:

arro3/pyproject.toml

Line 8 in da00c6c

requires-python = ">=3.9"

So this will have to be a future breaking release (i.e. minor bump to 3.10). Or maybe removing support for a python version doesn't require a minor bump 🤷‍♂️