[css-images-4] Remove issue about lengths in <angular-color-stop>, because it has accumulated no interest.

Author: tabatkins

css-images-4/Overview.bs

@@ -1375,9 +1375,6 @@ Gradient Color-Stops</h3>
 		</pre>
 	</div>
 
-	<p class='issue'>
-		Are lengths useful in <<angular-color-stop>>, for a given gradient circle?
-
 	<p class='issue'>
 		This is past the complexity point where it can be easily understood with just prose.
 		Add a diagram illustrating the possibilities,