Enable RL sync by default on iOS

components/reading_list/reading_list_pref_names.cc

Index: components/reading_list/reading_list_pref_names.cc
diff --git a/components/reading_list/reading_list_pref_names.cc b/components/reading_list/reading_list_pref_names.cc
deleted file mode 100644
index 5fd9c59fcd13edebe60107ff2e584494905bbc40..0000000000000000000000000000000000000000
--- a/components/reading_list/reading_list_pref_names.cc
+++ /dev/null
@@ -1,15 +0,0 @@
-// Copyright 2016 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.
-
-#include "components/reading_list/reading_list_pref_names.h"
-
-namespace reading_list {
-namespace prefs {
-
-// Boolean to track if some reading list entries have never been seen on this
-// device. Not synced.
-const char kReadingListHasUnseenEntries[] = "reading_list.has_unseen_entries";
-
-}  // namespace prefs
-}  // namespace reading_list