fixup! Switch blink::ContainerNode to use new downcast helpers

This CL removes unwanted comment from styled_markup_serializer.cc

Bug: 891908
Change-Id: I97d47cc28cb5a20b98f59bed6f69ba87e412ec3a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1617564Reviewed-by: Christian Biesinger <cbiesinger@chromium.org>
Commit-Queue: Abhijeet Kandalkar <abhijeet@igalia.com>
Cr-Commit-Position: refs/heads/master@{#661269}

third_party/blink/renderer/core/editing/serializers/styled_markup_serializer.cc

@@ -300,7 +300,6 @@ String StyledMarkupSerializer<Strategy>::CreateMarkup() {
     }
   } else if (should_append_parent_tag) {
     EditingStyle* style = traverser.CreateInlineStyleIfNeeded(*last_closed_);
-    // traverser.WrapWithNode(*To<ContainerNode>(last_closed_.Get()), style);
     traverser.WrapWithNode(To<ContainerNode>(*last_closed_), style);
   }