Fix build: remove redundant license classifier (PEP 639)

Newer setuptools enforces PEP 639 and rejects having both
license = "MIT" and a License :: classifier. Remove the classifier
since the license field already covers it.

Author: bojieli

pyproject.toml

@@ -14,7 +14,6 @@ keywords = ["pine-assistant", "pine", "ai", "customer-service", "sdk", "socketio
 classifiers = [
     "Development Status :: 3 - Alpha",
     "Intended Audience :: Developers",
-    "License :: OSI Approved :: MIT License",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.10",
     "Programming Language :: Python :: 3.11",