Remove python dependency upper bound

[yajo]

Python dependency has an upper bound: https://github.com/mtkennerly/dunamai/blob/8a16c30124a1421d62ee8d492f77e3a63b01bd9c/pyproject.toml#L24

https://iscinumpy.dev/post/bound-version-constraints/ explains why this is bad.

Would you mind to please remove that and just use python = ">=3.5"?

Thanks!

[mtkennerly]

While I don't agree with that article's points about Semantic Versioning, I do agree that:

• Python itself doesn't follow Semantic Versioning
• The flat nature of site-packages makes it hard to deal with conflicting version bounds

While doing some research, I also found these discussions helpful:

• https://discuss.python.org/t/requires-python-upper-limits/12663
• https://github.com/python-poetry/poetry/issues/6884

I'll relax the bounds to use >=.