Fix struct traits test deps and target visibility.

ash/public/cpp/BUILD.gn

 # 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.
 
 # C++ headers and sources that can be used outside ash.
 component("ash_public_cpp") {
   sources = [
     "ash_public_export.h",
     "mus_property_mirror_ash.cc",
     "mus_property_mirror_ash.h",
@@ skipping 30 matching lines @@
 }
 
 source_set("unit_tests") {
   testonly = true
   sources = [
     "shelf_struct_traits_unittest.cc",
   ]
 
   deps = [
     ":ash_public_cpp",
-
-    # TODO(crbug.com/702397): Rely on :ash_public_cpp for this instead.
-    "//ash/public/interfaces:interfaces_internal",
     "//base",
     "//testing/gtest",
     "//ui/gfx:test_support",
   ]
 }