Update hasCrossSiteAncestor.md

Update language to include reference to nonce

proposals/hasCrossSiteAncestor.md

@@ -114,7 +114,7 @@ A Promise that will be fulfilled with a `Cookie.partitionKey` object that matche
 ##### Error conditions
 - If host permissions are not granted for the document whose partitionkey is getting queried an error will be returned.
 - When the parameters passed do not correspond to an existing frame, an error will be returned.
-- If the partitionKey that would be associated with the frame can not be serialized an error will be returned. This can happen when the origin associated with the topLevelSite is opaque. 
+- If the partitionKey that would be associated with the frame can not be serialized an error will be returned. This can happen when the origin associated with the topLevelSite is opaque or if the underlying key associated with the frame has a nonce. 
 
 ### New Permissions
 No new permissions are required.