Cleanup: remove the namespace-level nodoc annotations from Extension API

chrome/common/extensions/api/music_manager_private.idl

 // Copyright 2013 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.
 
 // musicManagerPrivate.
-[nodoc] namespace musicManagerPrivate {
+namespace musicManagerPrivate {
 
   callback GetDeviceIdCallback = void (DOMString device_id);
 
   interface Functions {
     // Returns an identifier stable across users and reboots.
     //
     // |callback| : Called with the stable identifier value.
     static void getDeviceId(GetDeviceIdCallback callback);
   };
 };