[JOSS REVIEW] Adopt PEP 639 for license #176
Description
The license information detailed in the pyproject.toml is inaccurate:
license = {text = "BSD License, Version 3-Clause"},
The license should make use of the SPDX code using the PEP 639 standard (supported by setuptools >=77.0):
license = "BSD-3-Clause",
license-files = ["LICENSE.txt"],
At the same time, the license classifier ("License :: OSI Approved :: BSD License",) can be removed (now deprecated).
Resources: https://peps.python.org/pep-0639/
Context: openjournals/joss-reviews#9688