Enable use_once_callback on mojom GN rule by default

components/discardable_memory/public/interfaces/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.
 
 import("//mojo/public/tools/bindings/mojom.gni")
 import("//testing/test.gni")
 
 mojom("interfaces") {
   sources = [
     "discardable_shared_memory_manager.mojom",
   ]
 
   import_dirs = [
     get_path_info("../../../..", "abspath"),
     "//mojo/services",
   ]
-
-  use_once_callback = true
 }