[css-grid-2] Remind that abspos forces idnependent formatting context. #7124

Author: fantasai

css-grid-2/Overview.bs

@@ -1570,7 +1570,8 @@ Explicit Track Sizing: the 'grid-template-rows' and 'grid-template-columns' prop
 			If there is no [=parent grid=],
 			or if the [=grid container=] is otherwised forced
 			to establish an [=independent formatting context=]
-			(for example, due to [=layout containment=] [[CSS-CONTAIN-2]]),
+			(for example, due to [=layout containment=] [[CSS-CONTAIN-2]]
+			or [=absolute positioning=] [[CSS-POSITION-3]]),
 			the [=used value=] is
 			the initial value, ''grid-template-rows/none'',
 			and the [=grid container=] is not a [=subgrid=].