Fix dependencies

vendor/golang.org/x/net/icmp/ipv6.go

@@ -1,23 +0,0 @@
-// Copyright 2013 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package icmp
-
-import (
-	"net"
-
-	"golang.org/x/net/internal/iana"
-)
-
-const ipv6PseudoHeaderLen = 2*net.IPv6len + 8
-
-// IPv6PseudoHeader returns an IPv6 pseudo header for checksum
-// calculation.
-func IPv6PseudoHeader(src, dst net.IP) []byte {
-	b := make([]byte, ipv6PseudoHeaderLen)
-	copy(b, src.To16())
-	copy(b[net.IPv6len:], dst.To16())
-	b[len(b)-1] = byte(iana.ProtocolIPv6ICMP)
-	return b
-}