chore: apply pep 639 (#220)

Fixes #217

Author: afuetterer

pyproject.toml

@@ -20,14 +20,14 @@ keywords = [
   "repositories",
   "research data",
 ]
-license = { text = "MIT" }
+license = "MIT"
+license-files = [ "LICENSE" ]
 authors = [
   { name = "Heinz-Alexander Fütterer" },
 ]
 requires-python = ">=3.10"
 classifiers = [
   "Development Status :: 1 - Planning",
-  "License :: OSI Approved :: MIT License",
   "Operating System :: OS Independent",
   "Programming Language :: Python",
   "Programming Language :: Python :: 3 :: Only",