remove ref machine learned entity

Author: diberry

articles/cognitive-services/LUIS/toc.yml

@@ -305,8 +305,6 @@
     displayName: Calendar, Communication,Email,HomeAutomation,Note,Places, RestaurantReservation,ToDo,Utilities,Weather,Web
   - name: Custom entity reference
     items: 
-    - name: Machine-learned entity
-      href: reference-entity-machine-learned-entity.md
     - name: Composite entity
       href: reference-entity-composite.md
     - name: List entity