remove unused variable

transport/internet/kcp/dialer.go

@@ -1,7 +1,6 @@
 package kcp
 
 import (
-	"errors"
 	"math/rand"
 	"net"
 
@@ -10,10 +9,6 @@ import (
 	"github.com/v2ray/v2ray-core/transport/internet"
 )
 
-var (
-	ErrUnknownDestination = errors.New("Destination IP can't be resolved.")
-)
-
 func DialKCP(src v2net.Address, dest v2net.Destination) (internet.Connection, error) {
 	udpDest := v2net.UDPDestination(dest.Address(), dest.Port())
 	log.Info("Dialling KCP to ", udpDest)