Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/ProgressElement.dartdoc

Index: lib/html/doc/interface/ProgressElement.dartdoc
diff --git a/lib/html/doc/interface/ProgressElement.dartdoc b/lib/html/doc/interface/ProgressElement.dartdoc
deleted file mode 100644
index a8a9f19958a91065e60a425489f745db70cd6459..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/ProgressElement.dartdoc
+++ /dev/null
@@ -1,25 +0,0 @@
-// 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 HTMLProgressElement
-interface ProgressElement extends Element default _Elements {
-
-  ProgressElement();
-
-  /** @domName HTMLProgressElement.labels */
-  final NodeList labels;
-
-  /** @domName HTMLProgressElement.max */
-  num max;
-
-  /** @domName HTMLProgressElement.position */
-  final num position;
-
-  /** @domName HTMLProgressElement.value */
-  num value;
-}