Handle showing tour modal when Content Drip panel is at the bottom

[Imran92]

When taking the lesson tour, if the lesson does not have questions or content, the content drip panel falls in the background of the Lesson Tour modal. As both of them have white background, it doesn't look very good.

We have to find a solution to make it work.

Some suggestions are-

1. Don't show content drip panel when Tour Modal is on screen
2. Move Tour modal to upper left corner instead of bottom left so that it doesn't have that instruction
3. Position it above the Content Drip panel

https://github.com/Automattic/sensei/assets/6820724/8e08fd1e-bc66-48de-942f-61842ed94db8

Tough Content Drip is in Pro, I'm creating the issue in Core because it'll probably need to handled from the lesson tour. But feel free to move this issue to Pro if the solution is implemented there.