Unlock kill trackers for InsertSocketPlugFree

[justrealmilk]

{
    "ErrorCode": 1678,
    "ThrottleSeconds": 0,
    "ErrorStatus": "DestinySocketActionNotAllowed",
    "Message": "You cannot perform that change through Bungie.net at this time.",
    "MessageData": {
        "request.plug.socketIndex": "The socketIndex 9 referred to a socket type 1282012138, which has been blocked for 'free' socket actions.  You cannot perform the InsertPlugFree action on this socket."
    }
}