change topo_implementation default value (#4869)
change topo_implementation default value (#4869)

* change topo_implementation default value

Signed-off-by: Win-Man <7c6551885244447094d9e7fb412a5bd42169563a@qq.com>

* change the default value of topo_implementation to empty

enisoc/vitess,tinyspeck/vitess,vitessio/vitess,mahak/vitess,tinyspeck/vitess,davygeek/vitess,tinyspeck/vitess,davygeek/vitess,davygeek/vitess,tinyspeck/vitess,vitessio/vitess,davygeek/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,davygeek/vitess,enisoc/vitess,enisoc/vitess,mahak/vitess,enisoc/vitess,davygeek/vitess,enisoc/vitess,tinyspeck/vitess,enisoc/vitess,mahak/vitess,davygeek/vitess,vitessio/vitess,vitessio/vitess,mahak/vitess,tinyspeck/vitess,mahak/vitess,vitessio/vitess,mahak/vitess,enisoc/vitess,mahak/vitess,vitessio/vitess,tinyspeck/vitess