remove unused utils.GetByteOrder

This function was needed when we supported both Q039 (using big endian
encoding) and ealier versions (using little endian encoding).

internal/utils/byteorder.go

@@ -3,8 +3,6 @@ package utils
 import (
 	"bytes"
 	"io"
-
-	"github.com/lucas-clemente/quic-go/internal/protocol"
 )
 
 // A ByteOrder specifies how to convert byte sequences into 16-, 32-, or 64-bit unsigned integers.
@@ -25,9 +23,3 @@ type ByteOrder interface {
 	ReadUfloat16(io.ByteReader) (uint64, error)
 	WriteUfloat16(*bytes.Buffer, uint64)
 }
-
-// GetByteOrder gets the ByteOrder to represent values on the wire
-// from QUIC 39, values are encoded in big endian, before that in little endian
-func GetByteOrder(v protocol.VersionNumber) ByteOrder {
-	return BigEndian
-}