use batchElem from rpc client

pkg/core/rpc_client.go

@@ -2,12 +2,12 @@ package core
 
 import (
 	"context"
-	"github.com/ethereum/go-ethereum/rpc"
+	"github.com/vulcanize/vulcanizedb/pkg/geth/client"
 )
 
 type RpcClient interface {
 	CallContext(ctx context.Context, result interface{}, method string, args ...interface{}) error
-	BatchCall(batch []rpc.BatchElem) error
+	BatchCall(batch []client.BatchElem) error
 	IpcPath() string
 	SupportedModules() (map[string]string, error)
 }