Update license tagging

[SebastianSchildt]

We are using an outdated way to declare the package licence, meanwhile Python supports an explicit SPDX identifier.

See this warning during build

#31 41.40 /tmp/build-env-sedgnv9l/lib/python3.10/site-packages/setuptools/dist.py:759: SetuptoolsDeprecationWarning: License classifiers are deprecated.
#31 41.40 !!
#31 41.40 
#31 41.40         ********************************************************************************
#31 41.40         Please consider removing the following classifiers in favor of a SPDX license expression:
#31 41.40 
#31 41.40         License :: OSI Approved :: Apache Software License
#31 41.40 
#31 41.40         See https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license for details.
#31 41.40         ********************************************************************************
#31 41.40 
#31 41.40 !!
#31 41.40   self._finalize_license_expression()