Remove requires-python

[ucodery]

This copier always sets requires-python = ">=3.10", but it doesn't know what versions of python the (yet-to-be-crated) package will be compatible with.

Yes 3.10 is the lowest in-support version, but this is overly-restrictive to users. Especially for use in our tutorials, which use some very vanilla Python that would work all the way back to 3.3 I'd bet.

[Midnighter]

@blink1073 mentioned that myst requires 3.10

[ucodery]

Ah, so maybe conditional on {%- elif documentation == "sphinx" %}, which brings in the myst dep?

[lwasser]

Oh! This comes from myst? This requirement tripped some people up who were trying to install their package into an existing envt that ran 3.9!

[ucodery]

Also, this is adding an install floor to the project for a documentation dependency. At best, it should be a requirement of tool.hatch.envs.docs

[willingc]

Some discussion about classifiers: https://discuss.python.org/t/handling-stale-python-version-classifiers-for-low-churn-projects/66537/1