[css-overflow-4] Restrict float clipping to the block-end side

See w3c#13668

Author: frivoal

css-overflow-4/Overview.bs

@@ -1780,7 +1780,7 @@ Handling of Excess Content: the 'continue' property</h3>
 
 	Within a [=line-clamp container=],
 	floats which have not been made into [=invisible boxes=]
-	must be visually clipped to the [=content edge=]
+	must be visually clipped to the [=block-end=] [=content edge=]
 	of the [=line-clamp container=].
 	They do not introduce any clearance
 	that would make the [=line-clamp container=] increase its height,