Use PEP 639 license expressions in project metadata

Author: cdce8p

Diff for: pyproject.toml

@@ -1,6 +1,6 @@
 [build-system]
 # Minimum requirements for the build system to execute.
-requires = ["setuptools>=61.2"]
+requires = ["setuptools>=77.0"]
 build-backend = "setuptools.build_meta"
 
 [project]
@@ -17,15 +17,15 @@ maintainers = [
     {name = 'Waylan Limberg', email = 'python.markdown@gmail.com'},
     {name = 'Isaac Muse'}
 ]
-license = {file = 'LICENSE.md'}
+license = "BSD-3-Clause"
+license-files = ["LICENSE.md"]
 requires-python = '>=3.9'
 dependencies = [
     "importlib-metadata>=4.4;python_version<'3.10'"
 ]
 keywords = ['markdown', 'markdown-parser', 'python-markdown', 'markdown-to-html']
 classifiers = [
     'Development Status :: 5 - Production/Stable',
-    'License :: OSI Approved :: BSD License',
     'Operating System :: OS Independent',
     'Programming Language :: Python',
     'Programming Language :: Python :: 3',