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: I79ab33f892303fedff26a30862142df3e97bcc4a
Story: #2002586
Task: #24319

zuul.d/project.yaml

@@ -15,8 +15,8 @@
 - project:
     templates:
       - check-requirements
-      - publish-openstack-sphinx-docs
+      - publish-openstack-docs-pti
-      - release-notes-jobs
+      - release-notes-jobs-python3
     check:
       jobs:
         - openstack-ansible-linters