Cleanup: remove non-standard retain_unknown_fields from .proto files

components/sync/protocol/client_debug_info.proto

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 //
 // Sync protocol for debug info clients can send to the sync server.
 
 syntax = "proto2";
 
 option optimize_for = LITE_RUNTIME;
-option retain_unknown_fields = true;
 
 package sync_pb;
 
 import "get_updates_caller_info.proto";
 import "sync_enums.proto";
 
 // Per-type hint information.
 message TypeHint {
   // The data type this hint applied to.
   optional int32 data_type_id = 1;
@@ skipping 136 matching lines @@
   // Whether cryptographer is ready to encrypt and decrypt data.
   optional bool cryptographer_ready = 2;
 
   // Cryptographer has pending keys which indicates the correct passphrase
   // has not been provided yet.
   optional bool cryptographer_has_pending_keys = 3;
 
   // Indicates client has dropped some events to save bandwidth.
   optional bool events_dropped = 4;
 }