make the license field PEP639 compatible (#559)

Author: gruebel

pyproject.toml

@@ -5,10 +5,10 @@ description = "Generate locked-down AWS IAM Policies"
 authors = [
     { name = "Kinnaird McQuade", email = "kinnairdm@gmail.com" }
 ]
-license = { file = "LICENSE" }
+license = "MIT"
+license-files = ["LICENSE"]
 keywords = ["aws", "iam", "roles", "policy", "policies", "privileges", "security"]
 classifiers = [
-    "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3 :: Only",
     "Programming Language :: Python :: 3.10",