build: Fix deprecated license specification format

Author: Yuki Kobayashi

pyproject.toml

@@ -3,14 +3,13 @@ name = "yamllint"
 description = "A linter for YAML files."
 readme = {file = "README.rst", content-type = "text/x-rst"}
 requires-python = ">=3.9"
-license = {text = "GPL-3.0-or-later"}
+license = "GPL-3.0-or-later"
 authors = [{name = "Adrien Vergé"}]
 keywords = ["yaml", "lint", "linter", "syntax", "checker"]
 classifiers = [
     "Development Status :: 5 - Production/Stable",
     "Environment :: Console",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: GNU General Public License v3 (GPLv3)",
     "Programming Language :: Python",
     "Topic :: Software Development",
     "Topic :: Software Development :: Debuggers",