Fix #133912: Outliner elements faded when contents filter is disabled

Actually a mistake in f4f2248a9c. `TE_CHILD_NOT_IN_COLLECTION`
flag is set on tree elements if they belong to different collection. Use
this flag instead to grey out the tree element.

Pull Request: https://projects.blender.org/blender/blender/pulls/133962

source/blender/editors/space_outliner/outliner_draw.cc

@@ -3273,7 +3273,7 @@ static bool element_should_draw_faded(const TreeViewContext &tvc,
                                BKE_view_layer_base_find((ViewLayer *)tvc.view_layer, (Object *)ob);
         const bool is_visible = (base != nullptr) &&
                                 (base->flag & BASE_ENABLED_AND_VISIBLE_IN_DEFAULT_VIEWPORT) &&
-                                !BLI_listbase_is_empty(&te->subtree);
+                                !(te->flag & TE_CHILD_NOT_IN_COLLECTION);
 
         return !is_visible;
       }