[nancy] remove srv-data server which is halted since many years

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

-{
-  "kind": "physical",
-  "network_adapters": {
-    "bmc": {
-      "ip": "172.17.79.16",
-      "mac": "F0:1F:AF:E1:99:E4",
-      "mounted": true
-    },
-    "default": {
-      "ip": "172.16.79.16",
-      "mac": "A0:36:9F:2C:5D:B8",
-      "mounted": true
-    }
-  },
-  "serial": "GCQ7NZ1",
-  "type": "server",
-  "uid": "srv-data",
-  "warranty": "2020-11"
-}
\ No newline at end of file