Revert "Migrate mistral-extra to zuul v3"
Revert "Migrate mistral-extra to zuul v3"

These jobs belong to project-config, they should not be added here.

This reverts commit a552b3cd7000e497a3687b9b54a1271b77d7f532.

Change-Id: I110315d3946ea8daafecd0fb7f5782e16d3125bf

openstack/mistral-extra,openstack/mistral-extra