Update classifiers to reflect stable (#2823)

Author: ichard26

setup.py

@@ -114,7 +114,7 @@ def find_python_files(base: Path) -> List[Path]:
     },
     test_suite="tests.test_black",
     classifiers=[
-        "Development Status :: 4 - Beta",
+        "Development Status :: 5 - Production/Stable",
         "Environment :: Console",
         "Intended Audience :: Developers",
         "License :: OSI Approved :: MIT License",