[css-grid] MAY -> MUST on fragmenting between columns per WG resolution

Author: fantasai

css-grid/Overview.bs

@@ -3990,7 +3990,6 @@ Fragmenting Grid Layout</h2>
 			and <a href="https://www.w3.org/TR/css3-break/#end-block">Class C break opportunities</a> occur
 			between the first/last row (column) and the grid container's content edges.
 			[[!CSS3-BREAK]]
-			UAs are not required to support fragmentation across the row axis.
 
 		<li>
 			When a grid container is continued after a break,