setup.cfg: update license, remove classifier

Use an SPDX license expression for license and remove the classifier, as
suggested by setuptools.

Signed-off-by: Kevin Locke <[email protected]>

Author: kevinoid

setup.cfg

@@ -8,10 +8,10 @@ friendly_name = Python Project Template
 version = attr: packagename.__version__
 description = Short description of this package and its purpose.
 long_description = file: README.rst
-# Note: license is only needed for deviations/exceptions to License classifier
-# https://packaging.python.org/guides/distributing-packages-using-setuptools/?highlight=keywords#license
+# license should be a valid SPDX license expression
+# https://packaging.python.org/en/latest/guides/writing-pyproject-toml/#license
 # Is also printed by `./setup.py --license`.  Match classifier where possible.
-license = MIT License
+license = MIT
 license_files = LICENSE.txt
 author = Kevin Locke
 author_email = [email protected]
@@ -28,7 +28,6 @@ project_urls =
 classifiers =
     Development Status :: 3 - Alpha
     Intended Audience :: Developers
-    License :: OSI Approved :: MIT License
     Operating System :: OS Independent
     Programming Language :: Python
     Programming Language :: Python :: 3