Fix #119254: Rebuild outliner tree after drop to scene operation

After drop to scene operation, notifiers are sent to redraw the tree but
it uses the old tree hierarchy. `RGN_DRAW_NO_REBUILD` flag prevented the
tree rebuilding in `outliner_build_tree`. To clear the flag, call
region_redraw function inside `scene_drop_invoke()`.

Pull Request: https://projects.blender.org/blender/blender/pulls/133253

source/blender/editors/space_outliner/outliner_dragdrop.cc

@@ -592,6 +592,7 @@ static int scene_drop_invoke(bContext *C, wmOperator * /*op*/, const wmEvent *ev
     }
   }
 
+  ED_region_tag_redraw(CTX_wm_region(C));
   DEG_relations_tag_update(bmain);
 
   DEG_id_tag_update(&scene->id, ID_RECALC_SELECT);