Fix outliner showing objects in collections instances.

It didn't do this before for groups, and while it could be useful this leads
to terrible performance when there are many instances.

source/blender/editors/space_outliner/outliner_tree.c

@@ -813,8 +813,11 @@ static void outliner_add_id_contents(SpaceOops *soops, TreeElement *te, TreeStor
 		}
 		case ID_GR:
 		{
-			Collection *collection = (Collection *)id;
-			outliner_add_collection_recursive(soops, collection, te);
+			/* Don't expand for instances, creates too many elements. */
+			if (!(te->parent && te->parent->idcode == ID_OB)) {
+				Collection *collection = (Collection *)id;
+				outliner_add_collection_recursive(soops, collection, te);
+			}
 		}
 		default:
 			break;