chore: remove deprecated license classifiers

Use an SPDX expression covering all instead.

https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license-and-license-files

Author: scop

setup.cfg

@@ -3,13 +3,10 @@ name = shfmt_py
 version = 3.12.0-2
 description = Shell source code formatter
 url = https://github.com/scop/pre-commit-shfmt
-# license here is for shfmt proper; Python packaging related files may have others, see their contents and classifiers below
-license = BSD 3-Clause
+# shfmt proper and Python packaging related files
+license = BSD 3-Clause AND Apache Software License AND MIT License
 classifiers =
     Intended Audience :: Developers
-    License :: OSI Approved :: Apache Software License
-    License :: OSI Approved :: BSD License
-    License :: OSI Approved :: MIT License
     Operating System :: MacOS
     Operating System :: Microsoft :: Windows
     Operating System :: POSIX :: Linux