Drop centos8s jobs from experimental pipeline
Drop centos8s jobs from experimental pipeline

This is a follow-up to [0], removing jobs also from experimental to
avoid unnecessary runs. Since zuul complains about an empty project
stanza, remove the whole block, it can always be restored from git
history if needed.

[0] I32bef531896777bfb463bb401ebba1d488a16bf9

Change-Id: If68d548957adb8c6584dcab4582ef8396cccf0b2

openstack/kolla,openstack/kolla