[ci_netconfig] Remove unused and outdated role

This role was part of the old effort to have a common
strategy to deploy VA/DTs and install_yamls deployments
but the approach drastically changed during its
development and it has never been used nor updated to
use the networking mapper.

Author: pablintino

ci/config/molecule.yaml

@@ -42,9 +42,6 @@
 - job:
     name: cifmw-molecule-ci_nmstate
     parent: cifmw-molecule-base-crc
-- job:
-    name: cifmw-molecule-ci_metallb
-    parent: cifmw-molecule-base-crc
 - job:
     name: cifmw-molecule-install_openstack_ca
     parent: cifmw-molecule-base-crc