`license` argument in setup.py is deprecated.

[IvanaGyro]

Here is the message from pip 25.1.1

SetuptoolsDeprecationWarning: License classifiers are deprecated.

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

          License :: OSI Approved :: GNU Lesser General Public License v3 or later (LGPLv3+)

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

As mentioned in #607, we seem accidentally adopt two licenses, here are the available license identifiers from the SPDX page for the two licenses.

For LGPL, there are five available identifiers

• LGPL-2.0-or-later
• LGPL-2.1-only
• LGPL-2.1-or-later
• LGPL-3.0-only
• LGPL-3.0-or-later

For Apache 2.0, the available identifier is Apache-2.0.