setuptools deprecation warnings for `pyproject.toml` license entry

[braingram]

I built rad with pip install -v . (while in a local clone of main at d30ee44).

The build used setuptools-78.1.0

I saw a few deprecation warnings that may all be related to the project.license usage:

rad/pyproject.toml

Lines 26 to 27 in d30ee44

	[project.license]
	file = "LICENSE"

  /private/var/folders/vk/4ry5_1zd2knfy0f8t63cdcsh0005g6/T/pip-build-env-7mll0xvm/overlay/lib/python3.12/site-packages/setuptools/config/_apply_pyprojecttoml.py:82: SetuptoolsDeprecationWarning: `project.license` as a TOML table is deprecated
  !!

          ********************************************************************************
          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.
          ********************************************************************************

  !!
    corresp(dist, value, root_dir)
  /private/var/folders/vk/4ry5_1zd2knfy0f8t63cdcsh0005g6/T/pip-build-env-7mll0xvm/overlay/lib/python3.12/site-packages/setuptools/config/_apply_pyprojecttoml.py:61: SetuptoolsDeprecationWarning: License classifiers are deprecated.
  !!

          ********************************************************************************
          Please consider removing the following classifiers in favor of a SPDX license expression:

          License :: OSI Approved :: BSD License

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

  !!
    dist._finalize_license_expression()
  /private/var/folders/vk/4ry5_1zd2knfy0f8t63cdcsh0005g6/T/pip-build-env-7mll0xvm/overlay/lib/python3.12/site-packages/setuptools/dist.py:759: SetuptoolsDeprecationWarning: License classifiers are deprecated.
  !!

          ********************************************************************************
          Please consider removing the following classifiers in favor of a SPDX license expression:

          License :: OSI Approved :: BSD License

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

  !!
    self._finalize_license_expression()

[braingram]

Looks like a setuptools v77 change: https://setuptools.pypa.io/en/latest/history.html#id25

Deprecated project.license as a TOML table in pyproject.toml. Users are expected to move towards using project.license-files and/or SPDX expressions (as strings) in project.license. See PEP 639. (#4840)

[WilliamJamieson]

Fixed by #588