remove unnecessary import

transport/internet/kcp/segment.go

@@ -3,7 +3,6 @@ package kcp
 import (
 	"v2ray.com/core/common"
 	"v2ray.com/core/common/alloc"
-	_ "v2ray.com/core/common/log"
 	"v2ray.com/core/common/serial"
 )