"Using Viewports" is outdated

[KoBeWi]

Your Godot version:
4.0

Issue description:

The page says "Up to date", but it's not. At least the "Capture part: https://docs.godotengine.org/en/stable/tutorials/rendering/viewports.html#capture

The code sample uses old ImageTexture creation code. Also pretty sure vertical flip is not necessary in Vulkan.

URL to the documentation page:

https://docs.godotengine.org/en/stable/tutorials/rendering/viewports.html