[nancy][graffiti] fix error in IP address allocated to graffiti-pdu3 and 4

data/grid5000/sites/nancy/pdus/graffiti-pdu3.json

 {
-  "ip": "172.17.79.228",
+  "ip": "172.17.79.231",
   "mac": "28:29:86:12:27:FF",
   "model": "AP8653",
   "ports": {

data/grid5000/sites/nancy/pdus/graffiti-pdu4.json

 {
-  "ip": "172.17.79.229",
+  "ip": "172.17.79.232",
   "mac": "28:29:86:10:0E:B4",
   "model": "AP8653",
   "ports": {

input/grid5000/sites/nancy/pdus.yaml

@@ -131,9 +131,9 @@ pdus:
     mac: 28:29:86:10:0E:8C
 
   graffiti-pdu3:
-    ip: 172.17.79.228
+    ip: 172.17.79.231
     mac: 28:29:86:12:27:FF
 
   graffiti-pdu4:
-    ip: 172.17.79.229
+    ip: 172.17.79.232
     mac: 28:29:86:10:0E:B4