setup.cfg: remove deprecated classifier

Fixes the following warning:

/usr/lib/python3.13/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 :: Apache Software License

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

!!

Author: yegorich

setup.cfg

@@ -33,8 +33,6 @@ classifiers =
 
   Intended Audience :: Developers
 
-  License :: OSI Approved :: Apache Software License
-
   Programming Language :: Cython
   Programming Language :: Python
   Programming Language :: Python :: 3