Physics introduction: should you multiply velocity by delta before calling move_and_slide() or not?

**stable (4.0)**

**Issue description:** there is a warning in the docs that states: `move_and_slide()` automatically includes the timestep in its calculation, so you should not multiply the velocity vector by `delta`., but the code that follows seems to do the opposite. As a beginner I find it a bit confusing.
The piece of code that puzzles me is:
```
func _physics_process(delta):
velocity.y += gravity * delta
get_input()
move_and_slide()
```
Why `gravity` is multiplied by `delta`?

**URL to the documentation page (if already existing):** [link](https://docs.godotengine.org/en/stable/tutorials/physics/physics_introduction.html)