Fix dependencies

vendor/google.golang.org/protobuf/internal/strs/strings_pure.go

@@ -1,27 +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.
-
-// +build purego appengine
-
-package strs
-
-import pref "google.golang.org/protobuf/reflect/protoreflect"
-
-func UnsafeString(b []byte) string {
-	return string(b)
-}
-
-func UnsafeBytes(s string) []byte {
-	return []byte(s)
-}
-
-type Builder struct{}
-
-func (*Builder) AppendFullName(prefix pref.FullName, name pref.Name) pref.FullName {
-	return prefix.Append(name)
-}
-
-func (*Builder) MakeString(b []byte) string {
-	return string(b)
-}