[css-overflow-4] Remove idle musing from the spec

Author: frivoal

css-overflow-4/Overview.bs

@@ -720,8 +720,6 @@ Indicating Block-Axis Overflow: the 'block-ellipsis' property</h3>
 
 	Note: See ''continue: discard'' for a way to generate boxes with such a [=region break=].
 
-	ISSUE: Should this apply to other types of fragmentation breaks (e.g. pages, columns)?
-
 	The inserted content is called the <dfn>block overflow ellipsis</dfn>.
 	Values have the following meanings: