Integrate_forces() example missing the point

V4.3

The code snippet meant to demonstrate how `_integrate_forces()` can be used to make direct changes to Rigidbody properties, that otherwise would interfere with the physics simulation, doesn't overwrite any of those properties. In fact, all the code could run in `_physics_process()` as well, so it's completely missing the point of the description above.

As an example it could change the `rotation` of the body's state transform directly when steering. Then using `_integrate_forces()` would at least be necessary in this context.

[Docs Page](https://docs.godotengine.org/en/stable/tutorials/physics/physics_introduction.html#using-rigidbody2d)