Remove the notificationProvider extension API

chrome/common/extensions/api/BUILD.gn

 # Copyright 2015 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("//build/config/features.gni")
 import("//build/config/ui.gni")
 import("//chrome/common/features.gni")
 import("//extensions/features/features.gni")
 import("//media/media_options.gni")
 import("//tools/json_schema_compiler/json_features.gni")
@@ skipping 39 matching lines @@
   "hotword_private.idl",
   "i18n.json",
   "identity.idl",
   "identity_private.idl",
   "image_writer_private.idl",
   "inline_install_private.idl",
   "instance_id.json",
   "language_settings_private.idl",
   "manifest_types.json",
   "media_galleries.idl",
-  "notification_provider.idl",
   "notifications.idl",
   "omnibox.json",
   "page_capture.json",
   "passwords_private.idl",
   "permissions.json",
   "preferences_private.json",
   "resources_private.idl",
   "screenlock_private.idl",
   "sessions.json",
   "settings_private.idl",
@@ skipping 196 matching lines @@
 }
 
 group("extensions_features") {
   public_deps = [
     ":api_features",
     ":behavior_features",
     ":manifest_features",
     ":permission_features",
   ]
 }