Remove bootstrap_nodeid group var

The bootstrap_nodeid group var is no longer needed coming out of Heat
because it's value can be calculated entirely with the Ansible jinja2
template.

Change-Id: I7406cb4d79a5fd988482fc679bb94bc2d33218c2

overcloud.j2.yaml

@@ -857,10 +857,6 @@ resources:
     type: OS::Heat::Value
     properties:
       value:
-        bootstrap_nodeid:
-          yaql:
-            expression: coalesce($.data, []).where(not isEmpty($)).first()
-            data: {get_attr: [{{role.name}}, hostname]}
         ctlplane_subnet_cidr:
           yaql:
             expression: coalesce($.data, []).where(not isEmpty($)).first().split('/')[-1]