Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/FormElement.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 HTMLFormElement
-interface FormElement extends Element {
-
-  /** @domName HTMLFormElement.acceptCharset */
-  String acceptCharset;
-
-  /** @domName HTMLFormElement.action */
-  String action;
-
-  /** @domName HTMLFormElement.autocomplete */
-  String autocomplete;
-
-  /** @domName HTMLFormElement.encoding */
-  String encoding;
-
-  /** @domName HTMLFormElement.enctype */
-  String enctype;
-
-  /** @domName HTMLFormElement.length */
-  final int length;
-
-  /** @domName HTMLFormElement.method */
-  String method;
-
-  /** @domName HTMLFormElement.name */
-  String name;
-
-  /** @domName HTMLFormElement.noValidate */
-  bool noValidate;
-
-  /** @domName HTMLFormElement.target */
-  String target;
-
-  /** @domName HTMLFormElement.checkValidity */
-  bool checkValidity();
-
-  /** @domName HTMLFormElement.reset */
-  void reset();
-
-  /** @domName HTMLFormElement.submit */
-  void submit();
-}