Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/HRElement.dartdoc

Index: lib/html/doc/interface/HRElement.dartdoc
diff --git a/lib/html/doc/interface/HRElement.dartdoc b/lib/html/doc/interface/HRElement.dartdoc
deleted file mode 100644
index b990d05bff3f73f33e5e970901948b78c6d6914d..0000000000000000000000000000000000000000
--- a/lib/html/doc/interface/HRElement.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 HTMLHRElement
-interface HRElement extends Element default _Elements {
-
-  HRElement();
-
-  /** @domName HTMLHRElement.align */
-  String align;
-
-  /** @domName HTMLHRElement.noShade */
-  bool noShade;
-
-  /** @domName HTMLHRElement.size */
-  String size;
-
-  /** @domName HTMLHRElement.width */
-  String width;
-}