Fix typo in the range-key docs

[DawidNiezgodka]

There is a typo in the docs about the range key, namely here:

query {
    findUserPurchasesInTime(id: "2", timestampFrom: 1, timestampTo: 4) {
    productId,
    price
    {
        total
    }
  }
}

It should be userId and not id