Remove ignore portion of tox.ini

In the latest hacking update a few rules were dropped, and we no
longer have to ignore these rules in our tox.ini.

Change-Id: Id38a1497019c7fe2d4ad8567f1c0c8d229951751

Author: Steve Martinelli

tox.ini

@@ -34,6 +34,5 @@ downloadcache = ~/cache/pip
 commands = python setup.py build_sphinx
 
 [flake8]
-ignore = H305,H307,H402,H904
 show-source = True
 exclude =  .venv,.git,.tox,dist,doc,*openstack/common*,*lib/python*,*egg,build,tools