Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/MeterElement.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 HTMLMeterElement
-interface MeterElement extends Element default _Elements {
-
-  MeterElement();
-
-  /** @domName HTMLMeterElement.high */
-  num high;
-
-  /** @domName HTMLMeterElement.labels */
-  final NodeList labels;
-
-  /** @domName HTMLMeterElement.low */
-  num low;
-
-  /** @domName HTMLMeterElement.max */
-  num max;
-
-  /** @domName HTMLMeterElement.min */
-  num min;
-
-  /** @domName HTMLMeterElement.optimum */
-  num optimum;
-
-  /** @domName HTMLMeterElement.value */
-  num value;
-}