Updated license classifier replacing deprecated one

Author: ritwik-g

pyproject.toml

@@ -16,7 +16,7 @@ keywords = ["unstract cli apps sdk"]
 classifiers = [
     "Development Status :: 4 - Beta",
     "Intended Audience :: Developers",
-    "License :: MIT",
+    "License-Expression :: MIT",
     "Operating System :: POSIX :: Linux",
     "Operating System :: MacOS :: MacOS X",
     "Operating System :: Microsoft :: Windows",