Fix dependencies

vendor/golang.org/x/net/http/httpguts/guts.go

@@ -1,50 +0,0 @@
-// Copyright 2018 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 httpguts provides functions implementing various details
-// of the HTTP specification.
-//
-// This package is shared by the standard library (which vendors it)
-// and x/net/http2. It comes with no API stability promise.
-package httpguts
-
-import (
-	"net/textproto"
-	"strings"
-)
-
-// ValidTrailerHeader reports whether name is a valid header field name to appear
-// in trailers.
-// See RFC 7230, Section 4.1.2
-func ValidTrailerHeader(name string) bool {
-	name = textproto.CanonicalMIMEHeaderKey(name)
-	if strings.HasPrefix(name, "If-") || badTrailer[name] {
-		return false
-	}
-	return true
-}
-
-var badTrailer = map[string]bool{
-	"Authorization":       true,
-	"Cache-Control":       true,
-	"Connection":          true,
-	"Content-Encoding":    true,
-	"Content-Length":      true,
-	"Content-Range":       true,
-	"Content-Type":        true,
-	"Expect":              true,
-	"Host":                true,
-	"Keep-Alive":          true,
-	"Max-Forwards":        true,
-	"Pragma":              true,
-	"Proxy-Authenticate":  true,
-	"Proxy-Authorization": true,
-	"Proxy-Connection":    true,
-	"Range":               true,
-	"Realm":               true,
-	"Te":                  true,
-	"Trailer":             true,
-	"Transfer-Encoding":   true,
-	"Www-Authenticate":    true,
-}