Fix gridmap palette remaining invisible
Created by: Nehluxhes
Fix https://github.com/godotengine/godot/issues/32925
The bug appeared in commit https://github.com/godotengine/godot/pull/32095 where the palette is now hidden when the node exit the tree but is also never shown again. Correct me if I am wrong but there is no need to hide them anyway since another editor is displayed then (and there never was any displaying bug related to this before when the method was never called at all)