Update the "Development Status" classifier

Author: ArtyomVancyan

setup.cfg

@@ -27,7 +27,7 @@ license_files = LICENSE
 platforms = unix, linux, osx, win32
 classifiers =
     Operating System :: OS Independent
-    Development Status :: 3 - Alpha
+    Development Status :: 4 - Beta
     Framework :: FastAPI
     Programming Language :: Python
     Programming Language :: Python :: 3