Update license information according to PEP 639

Author: jlaine

pyproject.toml

@@ -5,7 +5,7 @@ requires = ["setuptools>61", "cython>=3.1.0a1,<4"]
 name = "av"
 description = "Pythonic bindings for FFmpeg's libraries."
 readme = "README.md"
-license = {text = "BSD-3-Clause"}
+license = "BSD-3-Clause"
 authors = [
     {name = "WyattBlue", email = "wyattblue@auto-editor.com"},
     {name = "Jeremy Lainé", email = "jeremy.laine@m4x.org"},
@@ -14,7 +14,6 @@ requires-python = ">=3.9"
 classifiers = [
     "Development Status :: 5 - Production/Stable",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: BSD License",
     "Natural Language :: English",
     "Operating System :: MacOS :: MacOS X",
     "Operating System :: POSIX",