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: I86b2aecb21ee9701e35e6143a599e05a23a37a07
Story: #2002586
Task: #24344

.zuul.yaml

@@ -2,8 +2,8 @@
     templates:
       - openstack-python-jobs-horizon
       - openstack-python35-jobs-horizon
-      - publish-openstack-sphinx-docs
-      - release-notes-jobs
+      - publish-openstack-docs-pti
+      - release-notes-jobs-python3
       - check-requirements
     check:
       jobs: