[css-overflow-4][editorial] Minor phrasing tweak (w3c#12293)

*Something* happens to the excess content (it overflows), so I find it
more natural to say that the behavior is the same as the initial value,
rather than to say there is no effect.

Author: frivoal

css-overflow-4/Overview.bs

@@ -1081,7 +1081,8 @@ Fragmentation of Overflow: the 'continue' property</h3>
 			This causes all content after the [=clamp point=] to be visually hidden, and to not be
 			taken into account for the box's [=automatic block size=].
 
-			This keyword has no effect on [=multicol containers=].
+			If the box is a [=multicol container=],
+			the behavior is the same as 'continue/auto'.
 	</dl>
 
 	<div class=example id=ex-continue-overflow>