Drop baremetal job template

https://review.openstack.org/#/c/619337/ switched the jobs to a noop for
master and since this file is branched we no longer need to keep this
template definition in this project.

Change-Id: Ic3447b4c26b01a8f060ab495050602cf137ba396

zuul.d/layout.yaml

@@ -5,6 +5,5 @@
       - openstack-python-jobs
       - openstack-python35-jobs
       - openstack-python36-jobs
-      - tripleo-multinode-baremetal-minimal
       - tripleo-multinode-container-minimal