Remove python version upper constraint

[chainyo]

Hi, this PR aims to remove the python upper version constraint <4.0 which is adding extra constraint for no reason and forces children project to adopt the unwanted poetry version notation or add this extra <4.0 constraint.

This would allow children project to avoid this useless warning

Note that the resolver complains only in poetry and not in rye, maybe rye knows python 4.0 is far from reality :hugs:

[thomasaarholt]

A bit niche, but I don't mind removing this constraint. Thanks! (And sorry for the late reply!)