[Sync::USS] Remove unnecessary TODO regarding copying bookmark meta_info

The directory implementation is different because directory keeps
a copy of the server data and then compares it to the newly version.
For USS, no copy is maintained and hence we have to create specifics
and push to the server when there is a local update.

Bug: 516866
Change-Id: Ic0a43b210866120c8ec209681e719d634fa10255
Reviewed-on: https://chromium-review.googlesource.com/1206410Reviewed-by: Mikel Astiz <mastiz@chromium.org>
Commit-Queue: Mohamed Amir Yosef <mamir@chromium.org>
Cr-Commit-Position: refs/heads/master@{#589865}

components/sync_bookmarks/bookmark_specifics_conversions.cc

@@ -23,9 +23,6 @@ namespace {
 void UpdateBookmarkSpecificsMetaInfo(
     const bookmarks::BookmarkNode::MetaInfoMap* metainfo_map,
     sync_pb::BookmarkSpecifics* bm_specifics) {
-  // TODO(crbug.com/516866): update the implementation to be similar to the
-  // directory implementation
-  // https://cs.chromium.org/chromium/src/components/sync_bookmarks/bookmark_change_processor.cc?l=882&rcl=f38001d936d8b2abb5743e85cbc88c72746ae3d2
   for (const std::pair<std::string, std::string>& pair : *metainfo_map) {
     sync_pb::MetaInfo* meta_info = bm_specifics->add_meta_info();
     meta_info->set_key(pair.first);