[Nantes] remove srv-data from ref repo

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

-{
-  "alias": [
-
-  ],
-  "kind": "physical",
-  "network_adapters": {
-    "bmc": {
-      "ip": "172.17.207.2",
-      "mac": "90:b1:1c:13:86:04"
-    },
-    "default": {
-      "ip": "172.16.207.2",
-      "mac": "a0:36:9f:0e:35:06"
-    }
-  },
-  "redfish": true,
-  "serial": "346ZG5J",
-  "type": "server",
-  "uid": "srv-data",
-  "warranty": "2019-11"
-}
\ No newline at end of file