[nancy][grdix] fix prod mac address

data/grid5000/sites/nancy/servers/grdix-srv.json

@@ -7,7 +7,7 @@
     },
     "default": {
       "ip": "172.16.79.31",
-      "mac": "bc:d7:a5:67:87:bb"
+      "mac": "9c:63:c0:aa:4e:08"
     }
   },
   "redfish": true,