Remove upper Python version limit

Signed-off-by: Philippe Ombredanne <pombredanne@nexb.com>

Author: pombredanne

setup.cfg

@@ -34,7 +34,7 @@ packages = find:
 include_package_data = true
 zip_safe = false
 
-python_requires = >=3.6.*, <4
+python_requires = >=3.6
 
 install_requires =
     attrs >= 18.1, !=20.1.0