Update project.license fields

[tkittel]

Seeing this warning with setuptools-based pyproject.toml files:

          ********************************************************************************
          Please use a simple string containing a SPDX expression for `project.license`. You can also use `project.license-files`. (Both options available on setuptools>=77.0.0).

          By 2026-Feb-18, you need to update your project and remove deprecated calls
          or your builds will no longer be supported.

          See https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license for details.
          ********************************************************************************

[tkittel]

An example for how it is done is in (note also license classifiers have been removed):

https://github.com/mctools/ncrystal-notebooks/blob/main/utilities/pyproject.toml