[toulouse][gw] Add forgotten ipv6 address to gw-toulouse

data/grid5000/sites/toulouse/network_equipments/gw-toulouse.json

 {
   "ip": "172.17.127.254",
+  "ip6": "2001:660:4406:900::ffff:ffff",
   "kind": "router",
   "linecards": [
     {

input/grid5000/sites/toulouse/networks/gw-toulouse.yaml

@@ -3,6 +3,7 @@ gw-toulouse:
   model: Temporary-Dell-OS6
   serial: unknown
   ip: 172.17.127.254
+  ip6: 2001:660:4406:900::ffff:ffff
   kind: router
   site: toulouse
   snmp_community: Unknown