[css-contain-3] Allow duplicate container names. w3c#7181

Author: lilles

css-contain-3/Overview.bs

@@ -477,7 +477,7 @@ Naming Query Containers: the 'container-name' property</h3>
 		Initial: none
 		Inherited: no
 		Applies to: all elements
-		Computed Value: a set of unique [=identifiers=]
+		Computed Value: the keyword ''none'', or an ordered list of [=identifiers=]
 		Animation type: not animatable
 	</pre>