[Bug12617] Remove gros-wattmetre1 & gros-wattmetre3

Related to bug12617.

Remove gros-wattmetre1 & gros-wattmetre3 from infra.

Removing theses two wattmetre broke the rake valid:homogeneity task, because nodes on gros-pdu2 have a wattmetre, and nodes on gros-pdu(1|3) doesn't have a wattmetre. So I added an exception in lib/refrepo/valid/data/homogeneity.rb so that it doesn't raise an error.

data/grid5000/sites/nancy/clusters/gros/nodes/gros-1.json

@@ -210,11 +210,6 @@
     "turboboost_enabled": true
   },
   "pdu": [
-    {
-      "kind": "wattmetre-only",
-      "port": 0,
-      "uid": "gros-wattmetre1"
-    },
     {
       "port": 1,
       "uid": "gros-pdu2"