switch documentation job to new PTI
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: If604a5e1c5daf478af093e8d107b5ecc17b3869b
Story: #2002586
Task: #24297

openstack/glance,openstack/glance,openstack/glance