demo: change back the protocol name, just comment the needed workaround

demo/terraform/vms.tf

@@ -27,7 +27,8 @@ resource "openstack_compute_secgroup_v2" "ping" {
   rule {
     from_port   = 128
     to_port     = 0
-    ip_protocol = "icmp"
+    # initial installation (bug in terraform): ip_protocol = "icmp"
+    ip_protocol = "ipv6-icmp"
     cidr        = "::/0"
   }
 }