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: I338fc71919a41ec890bcb5edd0552ec7eb680eb5
Story: #2002586
Task: #24327

Author: dhellmann

.zuul.yaml

@@ -482,7 +482,7 @@
     templates:
       - integrated-gate
       - integrated-gate-py35
-      - publish-openstack-sphinx-docs
+      - publish-openstack-docs-pti
     check:
       jobs:
         - devstack