fix: remove collection-entity through model post_delete signal handler

The indexing update is already handled by m2m_changed handler.

openedx/core/djangoapps/content_libraries/signal_handlers.py

@@ -162,16 +162,6 @@ def library_collection_entity_saved(sender, instance, created, **kwargs):
         _library_collection_component_changed(component)
 
 
-@receiver(post_delete, sender=CollectionPublishableEntity, dispatch_uid="library_collection_entity_deleted")
-def library_collection_entity_deleted(sender, instance, **kwargs):
-    """
-    Sends a CONTENT_OBJECT_ASSOCIATIONS_CHANGED event for components removed from a collection.
-    """
-    # Component.pk matches its entity.pk
-    component = get_component(instance.entity_id)
-    _library_collection_component_changed(component)
-
-
 @receiver(m2m_changed, sender=CollectionPublishableEntity, dispatch_uid="library_collection_entities_changed")
 def library_collection_entities_changed(sender, instance, action, pk_set, **kwargs):
     """