Remove explicit interface versions of dartdoc files.

lib/html/doc/interface/SVGFESpotLightElement.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 SVGFESpotLightElement
-interface SVGFESpotLightElement extends SVGElement {
-
-  /** @domName SVGFESpotLightElement.limitingConeAngle */
-  final SVGAnimatedNumber limitingConeAngle;
-
-  /** @domName SVGFESpotLightElement.pointsAtX */
-  final SVGAnimatedNumber pointsAtX;
-
-  /** @domName SVGFESpotLightElement.pointsAtY */
-  final SVGAnimatedNumber pointsAtY;
-
-  /** @domName SVGFESpotLightElement.pointsAtZ */
-  final SVGAnimatedNumber pointsAtZ;
-
-  /** @domName SVGFESpotLightElement.specularExponent */
-  final SVGAnimatedNumber specularExponent;
-
-  /** @domName SVGFESpotLightElement.x */
-  final SVGAnimatedNumber x;
-
-  /** @domName SVGFESpotLightElement.y */
-  final SVGAnimatedNumber y;
-
-  /** @domName SVGFESpotLightElement.z */
-  final SVGAnimatedNumber z;
-}