Remove unnecessary use_new_wrapper_types flag for some mojom targets.

ui/events/mojo/BUILD.gn

 # Copyright 2014 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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 
 mojom("interfaces") {
   sources = [
     "event.mojom",
     "event_constants.mojom",
     "keyboard_codes.mojom",
     "latency_info.mojom",
   ]
 
   public_deps = [
     "//mojo/common:common_custom_types",
     "//ui/gfx/geometry/mojo",
   ]
-
-  use_new_wrapper_types = false
 }
 
 mojom("test_interfaces") {
   testonly = true
   sources = [
     "traits_test_service.mojom",
   ]
 
   public_deps = [
     ":interfaces",
   ]
-
-  use_new_wrapper_types = false
 }
 
 source_set("struct_traits") {
   sources = [
     "latency_info_struct_traits.cc",
     "latency_info_struct_traits.h",
   ]
   deps = [
     ":interfaces_shared_cpp_sources",
     "//mojo/common",
     "//mojo/public/cpp/bindings",
     "//ui/events:events_base",
     "//ui/gfx/geometry/mojo:struct_traits",
   ]
 }