[luxembourg] Fix missing group_storage information for srv-data2

data/grid5000/sites/luxembourg/servers/srv-data2.json

@@ -3,6 +3,11 @@
     "srv-data-belval",
     "storage2"
   ],
+  "group_storage": {
+    "name": "storage2",
+    "rate": 200000000000,
+    "size": 25600000000000
+  },
   "kind": "physical",
   "network_adapters": {
     "bmc": {