Update to PEP 639 license metadata (#296)

Author: johnthagen

pyproject.toml

@@ -5,11 +5,11 @@ description = "Example Python project using best practices"
 authors = [
     { name = "John Hagen", email = "[email protected]" }]
 license = "MIT"
+license-files = ["LICENSE*"]
 readme = "README.md"
 classifiers = [
     "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Programming Language :: Python",
     "Programming Language :: Python :: 3",