[css-overflow-3] Rephrase the o-c-m:border-box on scroll containers to not imply something special about the 'act as padding box' thing.

Author: tabatkins

css-overflow-3/Overview.bs

@@ -622,8 +622,9 @@ Expanding Clipping Bounds: the 'overflow-clip-margin' property</h3>
 	* the [=overflow clip edge=] is clamped to stay within the element's [=padding box=].
 		(This does not affect the [=computed value|computed=] or [=used value=] of this property.)
 	* the ''overflow-clip-margin/border-box'' value
-		behaves as ''overflow-clip-margin/padding-box''
-		and ignores any specified offset.
+		ignores any specified offset
+		(and, due to the previous bullet point,
+		effectively acts as ''overflow-clip-margin/padding-box'')
 
 	Note: This property was previously defined to only affect ''overflow: clip''.
 	It now also affects [=scroll containers=],