Remove the mistake

Author: DifferentialOrange

test_helpers/msgpack.go

@@ -4,13 +4,7 @@
 package test_helpers
 
 import (
-	"io"
-
 	"gopkg.in/vmihailenco/msgpack.v2"
 )
 
 type encoder = msgpack.Encoder
-
-func newEncoder(w io.Writer) *encoder {
-	return msgpack.NewEncoder(w)
-}