[css-anchor-position][editorial] Make it clearer which referent the conditions have. w3c#10184

Author: tabatkins

css-anchor-position-1/Overview.bs

@@ -448,9 +448,9 @@ Anchor Relevance</h3>
 When determining whether an element |el| is [=relevant to the user=],
 if a descendant of |el| is a [=target anchor element=]
 for a positioned element
-who is not [=skipped contents|skipped=]
+(which is not [=skipped contents|skipped=]
 and whose containing block is not |el|
-or a descendant of |el|,
+or a descendant of |el|),
 then |el| must be considered [=relevant to the user=].
 
 Note: This means that, for example,