Remove python2 from project-template
Remove python2 from project-template

We're unwinding python2 testing. As part of doing that, remove
python2 from our zuul project-template which other people are
using to add tips jobs to their project.

Change-Id: I7d4b3f54cfd09d6a39b707f4a9a0bf4b2b9bca69

openstack/python-openstacksdk,stackforge/python-openstacksdk,openstack/python-openstacksdk,stackforge/python-openstacksdk