The docs about Camera3D display in Viewport is incorrect

**Your Godot version:**
4.4 latest

**Issue description:**

The docs about Camera3D in Viewport is confusing as described below they are [sharing a World3D by default](https://docs.godotengine.org/en/latest/tutorials/rendering/viewports.html#worlds) unless the Viewport set a different World3D. So actually both `CameraA` and `CameraB` will display `MeshA` and `MeshB`:

**URL to the documentation page:**
https://docs.godotengine.org/en/latest/tutorials/rendering/viewports.html#cameras-2d-3d