fix: use SPDX license expression in pyproject.toml

Author: chenguanzhou

pyproject.toml

@@ -7,13 +7,12 @@ name = "vectorizer-pro"
 version = "0.2.0"
 description = "Raster mask vectorization with topology-preserving simplification"
 readme = "README.md"
-license = {text = "MIT"}
+license = "MIT"
 authors = [{name = "Wuhan University CVEO Team"}]
 classifiers = [
     "Development Status :: 4 - Beta",
     "Intended Audience :: Developers",
     "Intended Audience :: Science/Research",
-    "License :: OSI Approved :: MIT License",
     "Operating System :: OS Independent",
     "Programming Language :: Python :: 3",
     "Programming Language :: Python :: 3.10",