docs(database): Removed object filtering comment

The query option is ignored when using objects, so referencing the list
docs is misleading.

Author: cartant

docs/2-retrieving-data-as-objects.md

@@ -188,6 +188,4 @@ this.item.subscribe(snapshot => {
 
 Because `FirebaseObjectObservable` synchronizes objects from the realtime database, sorting will have no effect for queries that are not also limited by a range. For example, when paginating you would provide a query with a sort and filter. Both the sort operation and the filter operation affect which subset of the data is returned by the query; however, because the resulting object is simply json, the sort order will not be preseved locally. Hence, for operations that require sorting, you are probably looking for a [list](3-retrieving-data-as-lists.md)
 
-For filtering response data see [](4-querying-lists.md) and repeat 'Object' to yourself everytime you read the word 'List'. 
-
 ###[Next Step: Retrieving data as lists](3-retrieving-data-as-lists.md)