Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/AudioBuffer.dartdoc

-// Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-// WARNING:
-//   This file contains documentation that is merged into the real source.
-//   Do not make code changes here.
-
-/// @domName AudioBuffer
-interface AudioBuffer {
-
-  /** @domName AudioBuffer.duration */
-  final num duration;
-
-  /** @domName AudioBuffer.gain */
-  num gain;
-
-  /** @domName AudioBuffer.length */
-  final int length;
-
-  /** @domName AudioBuffer.numberOfChannels */
-  final int numberOfChannels;
-
-  /** @domName AudioBuffer.sampleRate */
-  final num sampleRate;
-
-  /** @domName AudioBuffer.getChannelData */
-  Float32Array getChannelData(int channelIndex);
-}