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

Depends-On: https://review.openstack.org/#/c/594176/
Change-Id: I66df141b69103e1389a294b75daadb292673e8a0
Story: #2002586
Task: #24344

.zuul.yaml

@@ -2,9 +2,9 @@
     templates:
       - openstack-python-jobs
       - openstack-python35-jobs
-      - publish-openstack-sphinx-docs
+      - publish-openstack-docs-pti
       - check-requirements
-      - release-notes-jobs
+      - release-notes-jobs-python3
     check:
       jobs:
         - watcher-tempest-functional