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: I442a49ebd6028d25d2e7a1584bb063219a1fc297
Story: #2002586
Task: #24293

.zuul.yaml

@@ -1,10 +1,10 @@
 - project:
     templates:
       - check-requirements
-      - release-notes-jobs
+      - release-notes-jobs-python3
       - openstack-python-jobs
       - openstack-python35-jobs
-      - publish-openstack-sphinx-docs
+      - publish-openstack-docs-pti
     check:
       jobs:
         - openstack-tox-lower-constraints