Update docs/search/search_in_trash_reference.md

Author: adriendupuis

docs/search/search_in_trash_reference.md

@@ -7,6 +7,7 @@ page_type: reference
 
 When you [search for content items that are held in trash](search_api.md#searching-in-trash), you can apply only a limited subset of Search Criteria and Sort Clauses
 which can be used by `Ibexa\Contracts\Core\Repository\TrashService::findTrashItems`.
+Some sort clauses are exclusive to trash search.
 
 ## Search Criteria