switch documentation job to new PTI

This is a mechanically generated patch to switch the documentation
jobs to use the new PTI versions of the jobs as part of the
python3-first goal.

See the python3-first goal document for details:
https://governance.openstack.org/tc/goals/stein/python3-first.html

Fix tox.ini docs environment to build html and push to correct output
paths so that openstack-tox-docs jobs works.

Change-Id: Ib957e03d6b16d5fdb945e2be02ed75f0c7fa160b
Story: #2002586
Task: #24315

.zuul.yaml

@@ -13,10 +13,10 @@
 - project:
     templates:
       - openstack-python-jobs
-      - publish-openstack-sphinx-docs
+      - publish-openstack-docs-pti
       - check-requirements
       - openstack-python35-jobs
-      - release-notes-jobs
+      - release-notes-jobs-python3
     check:
       jobs:
         - openstack-tox-functional-with-sudo

tox.ini

@@ -41,7 +41,7 @@ basepython = python3
 deps =
   {env:CONSTRAINTS_OPT}
   -r{toxinidir}/doc/requirements.txt
-commands = sphinx-build -W doc/source doc/build
+commands = sphinx-build -W -b html doc/source doc/build/html
 
 [testenv:releasenotes]
 basepython = python3