Notch overlay should not show up while in non-UI Prefab Stage

[5argon]

The root is not a RectTransform so this is not a prefab stage for designing UI, yet the overlay didn't check for this. It should find some way to check if we are using the prefab design scene for UI or not. I haven't check if it is possible from the API, or we must observe the root and make hacky assumption?

(So ideally, I want to know which of the following scenes is being used. I think I saw a scene property somewhere while making the prefab mode support around the PrefabStage experimental API. But even if we know the scene, how to compare with this settings?)