Fix setup.cfg metadata

[h-mayorquin]

Hey guys, specifying metadata with dashes is deprecated on the last version of setuptools:

https://setuptools.pypa.io/en/stable/history.html?utm_source=chatgpt.com#bugfixes

This is causing people that want to build your package using the latest version of setuptools to fail:

NeuralEnsemble/python-neo#1660 (comment)

This PR should fix it.

[h-mayorquin]

It seems they did another release that postpones this but it is still a good idea to move forward with this.

[h-mayorquin]

This should fix #551 I think.

[coveralls]

coverage: 78.571%. remained the same
when pulling fa7eb9f on h-mayorquin:fix_setup_metadata
into 96271f1 on G-Node:master.

[jgrewe]

@h-mayorquin thank you

[h-mayorquin]

Thanks for the merge.

Btw, reading about this yesterday I realized that description_file is not even a valid metadata field. I think the correct field is long_description. Apparently, someone used it at some point and people have been copying it from other setup-like configurations but the correct

I suggest a move to pyproject.toml.