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: I5dbb420dfc8231c676ed096bda2ddf6448e3ee0e
Story: #2002586
Task: #24318

.zuul.yaml

@@ -14,7 +14,7 @@
 
 - project:
     templates:
-      - publish-openstack-sphinx-docs
+      - publish-openstack-docs-pti
     check:
       jobs:
         - openstack-helm-infra-linter