Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/HttpRequestException.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 XMLHttpRequestException
-interface HttpRequestException {
-
-  static final int ABORT_ERR = 102;
-
-  static final int NETWORK_ERR = 101;
-
-  /** @domName XMLHttpRequestException.code */
-  final int code;
-
-  /** @domName XMLHttpRequestException.message */
-  final String message;
-
-  /** @domName XMLHttpRequestException.name */
-  final String name;
-
-  /** @domName XMLHttpRequestException.toString */
-  String toString();
-}