Remove context2d.resetClip()

This is not shipping in any browsers, and was rejected by at least
WebKit and Chromium:

* https://bugs.webkit.org/show_bug.cgi?id=82801
* https://bugs.chromium.org/p/chromium/issues/detail?id=284600

There was a previous discussion about removal from the spec at
https://lists.w3.org/Archives/Public/public-canvas-api/2013JanMar/0017.html.

source

@@ -59917,7 +59917,6 @@ interface mixin <dfn>CanvasDrawPath</dfn> {
   void <span data-x="dom-context-2d-stroke">stroke</span>(<span>Path2D</span> path);
   void <span data-x="dom-context-2d-clip">clip</span>(optional <span>CanvasFillRule</span> fillRule = "<span data-x="dom-context-2d-fillRule-nonzero">nonzero</span>");
   void <span data-x="dom-context-2d-clip">clip</span>(<span>Path2D</span> path, optional <span>CanvasFillRule</span> fillRule = "<span data-x="dom-context-2d-fillRule-nonzero">nonzero</span>");
-  void <span data-x="dom-context-2d-resetClip">resetClip</span>();
   boolean <span data-x="dom-context-2d-isPointInPath">isPointInPath</span>(unrestricted double x, unrestricted double y, optional <span>CanvasFillRule</span> fillRule = "<span data-x="dom-context-2d-fillRule-nonzero">nonzero</span>");
   boolean <span data-x="dom-context-2d-isPointInPath">isPointInPath</span>(<span>Path2D</span> path, unrestricted double x, unrestricted double y, optional <span>CanvasFillRule</span> fillRule = "<span data-x="dom-context-2d-fillRule-nonzero">nonzero</span>");
   boolean <span data-x="dom-context-2d-isPointInStroke">isPointInStroke</span>(unrestricted double x, unrestricted double y);
@@ -63286,15 +63285,6 @@ v6DVT (also check for '- -' bits in the part above) -->
    </dd>
 
 
-   <dt><var>context</var> . <code subdfn data-x="dom-context-2d-resetClip">resetClip</code>()</dt>
-
-   <dd>
-
-    <p>Unconstrains the clipping region.</p>
-
-   </dd>
-
-
    <dt><var>context</var> . <code subdfn data-x="dom-context-2d-isPointInPath">isPointInPath</code>(<var>x</var>, <var>y</var> [, <var>fillRule</var> ] )</dt>
    <dt><var>context</var> . <code data-x="dom-context-2d-isPointInPath">isPointInPath</code>(<var>path</var>, <var>x</var>, <var>y</var> [, <var>fillRule</var> ] )</dt>
 
@@ -63382,10 +63372,6 @@ v6DVT (also check for '- -' bits in the part above) -->
        - maybe just support creating unions, intersections, and other -ions of paths
   -->
 
-  <p>The <dfn><code data-x="dom-context-2d-resetClip">resetClip()</code></dfn> method, when invoked,
-  must create a new <span>clipping region</span> that is the largest infinite surface. The new
-  clipping region replaces the current clipping region.</p>
-
   <hr>
 
   <p>The <dfn><code data-x="dom-context-2d-isPointInPath">isPointInPath()</code></dfn> method, when