Fix jobs

Non-voting jobs should never run in gate, remove the non-voting
requirements change - and the template as well.

Change docs building job to newer tox-docs which does "tox -e docs"
directly.

Update sphinx requirements for python3.

Depends-On:  https://review.opendev.org/660024
Change-Id: I4111e0f94ee5d0f1ed07743679e17b28ac70a518

.zuul.yaml

@@ -1,16 +1,11 @@
 - project:
     templates:
-      - check-requirements
       - openstack-python-jobs
       - openstack-python35-jobs
       - publish-to-pypi
     check:
       jobs:
-        - build-openstack-sphinx-docs:
+        - tox-docs:
             voting: false
         - requirements-check:
             voting: false
-    gate:
-      jobs:
-        - requirements-check:
-            voting: false

test-requirements.txt

@@ -2,6 +2,7 @@ flake8
 github3.py
 hacking
 mock
-sphinx>=1.6.5
+sphinx>=1.6.5,<2.0.0;python_version=='2.7'  # BSD
+sphinx>=1.6.5;python_version>='3.4'  # BSD
 stestr>=1.0.0
 testtools>=2.2.0