[css-multicol-2] Close issue about divergence with Håkon's spec

CSS-Figures has evolved, and now matches what we have here, so we
no longer need to worry about the difference.

Author: frivoal

css-multicol-2/Overview.bs

@@ -175,7 +175,6 @@ Spanning columns</h2>
 			</ul>
 			</div>
 
-			Issue: <a href="https://figures.spec.whatwg.org/">CSS Figures</a> has evolved into a different approach.
 		<dt><dfn>auto</dfn>
 		<dd>
 			The number of columns spanned by the element