[css-contain] Resolve bikeshed ambiguity

Author: frivoal

css-containment/Overview.bs

@@ -249,7 +249,7 @@ Style Containment</h3>
 		* 'bookmark-*'
 		* 'string-set'
 
-	2. The 'counter-increment', 'counter-set', 'flow-from', 'flow-into', and 'content' (for the purpose of ''open-quote''/etc values) properties must be <a>scoped</a> to the element's sub-tree.
+	2. The 'counter-increment', 'counter-set', 'flow-from', 'flow-into', and 'content' (for the purpose of ''content/open-quote''/etc values) properties must be <a>scoped</a> to the element's sub-tree.
 
 	A <dfn export local-lt="scoped">scoped property</dfn> has its effects scoped to a particular element or subtree.
 	It must act as if the scoping element was the root of the document