[css-conditional-5] container-names are not tree-scoped #12090 (#12720)

Per resolution in:

#12090 (comment)

Author: lilles

css-conditional-5/Overview.bs

@@ -589,6 +589,7 @@ Naming Query Containers: the 'container-name' property</h3>
 	specifies a list of <dfn export lt="query container name">query container names</dfn>.
 	These names can be used by ''@container'' rules
 	to filter which [=query containers=] are targeted.
+	Container names are not [=tree-scoped names=].
 
 	<dl dfn-for=container-name dfn-type=value>
 	<dt><dfn>none</dfn>