Remove doc8 from niceness check

- We're not at a point where the value proposition in consistent markup is
worth the pain in troubleshooting.
- Plus I think the current checks aren't sophisticated enough to replace humans.

Change-Id: Idb4e4acaf6b274024853847aa1d77324e251349f

test-requirements.txt

@@ -8,7 +8,6 @@ hacking>=0.10.0,<0.11
 
 beautifulsoup4
 Jinja2>=2.6  # BSD License (3 clause)
-doc8  # Apache-2.0
 openstack-doc-tools>=0.23
 sphinx>=1.1.2,!=1.2.0,!=1.3b1,<1.3
 openstackdocstheme>=1.0.3

tox.ini

@@ -25,7 +25,6 @@ commands = openstack-doc-test --check-links {posargs}
 [testenv:checkniceness]
 commands =
   openstack-doc-test --check-niceness {posargs}
-  doc8 doc
   flake8
 
 [testenv:checksyntax]