build: drop license from classifiers

Using the SPDX codes in pyproject.toml allow us to drop
the classifiers about licenses.

Pick-to: 6.9 6.8 6.5 6.2
Change-Id: Ia2e75012ff8ae707ef2fef6eb5cfcce43fe87f75
Reviewed-by: Shyamnath Premnadh <[email protected]>

Author: cmaureir

wheel_artifacts/pyproject.toml.base

@@ -21,10 +21,6 @@ classifiers = [
     "Environment :: X11 Applications :: Qt",
     "Environment :: Win32 (MS Windows)",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: GNU Lesser General Public License v3 (LGPLv3)",
-    "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
-    "License :: OSI Approved :: GNU General Public License v2 (GPLv2)",
-    "License :: Other/Proprietary License",
     "Operating System :: MacOS :: MacOS X",
     "Operating System :: POSIX",
     "Operating System :: POSIX :: Linux",