[css-grid] Remove issue (resolved https://lists.w3.org/Archives/Public/www-style/2016May/0231.html )

Author: fantasai

css-grid/Overview.bs

@@ -2347,11 +2347,6 @@ Subgrids</h2>
 				then that item is instead forced into (and limited to) the first (only) track in the subgrid.
 			</div>
 
-			Issue: Alternately,
-			since this is an error case,
-			should we instead make the item span the entire subgrid,
-			so it's more obvious that something is wrong?
-
 		<li>
 			The <a>subgrid</a> is always stretched in both dimensions:
 			the 'align-self'/'justify-self' properties on it are ignored,