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

Change-Id: Iee42c4b458e8ae8694efbee7e176cd2f8e8d49cd
Story: #2002586
Task: #24304

.zuul.yaml

@@ -2,10 +2,10 @@
     templates:
       - openstack-python-jobs
       - openstack-python35-jobs
-      - publish-openstack-sphinx-docs
+      - publish-openstack-docs-pti
       - check-requirements
       - lib-forward-testing
-      - release-notes-jobs
+      - release-notes-jobs-python3
     check:
       jobs:
         - openstack-tox-lower-constraints