Use UnpackIntoInterface instead of Unpack

After go-ethereum update from 1.9.10 to 1.10.1, we can no longer pass an
interface into Unpack function. An alternative is UnpackIntoInterface
that does the same as the previous version of Unpack.

Author: pdyraga

pkg/chain/ethereum/ethutil/ethutil.go

@@ -5,11 +5,12 @@ package ethutil
 import (
 	"context"
 	"fmt"
-	"github.com/keep-network/keep-common/pkg/chain/ethlike"
 	"io/ioutil"
 	"math/big"
 	"time"
 
+	"github.com/keep-network/keep-common/pkg/chain/ethlike"
+
 	"github.com/ipfs/go-log"
 
 	"github.com/ethereum/go-ethereum"
@@ -140,8 +141,7 @@ func CallAtBlock(
 		}
 	}
 
-	err = contractABI.Unpack(result, method, output)
-
+	err = contractABI.UnpackIntoInterface(result, method, output)
 	if err != nil {
 		return errorResolver.ResolveError(
 			err,