Simplify core/editing/OWNERS

Just refers to core/layout/OWNERS because the layout team is responsible
for the editing area now.
This CL has no production behavior changes.

Change-Id: I0d2668fe145bbb2201a8a677d823459daf5aaa7f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4327849
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Auto-Submit: Kent Tamura <tkent@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1115570}

third_party/blink/renderer/core/editing/OWNERS

@@ -1,2 +1 @@
-yosin@chromium.org
-xiaochengh@chromium.org
+file:../layout/OWNERS