`navigation_agent.set_velocity()` doesn't autocomplete in GDScript, so maybe replace it?

[AdriaandeJongh]

Your Godot version:
4.2.1

Issue description:
The docs mention navigation_agent.set_velocity(), but this doesn't autocomplete in GDScript because it's the setter of navigation_agent.velocity. The docs should probably be modified to use navigation_agent.velocity instead, so that noobs like me don't get confused as we are writing what's in the docs and the autocomplete makes it look like the method from the docs doesn't exist.

URL to the documentation page:
https://docs.godotengine.org/en/latest/tutorials/navigation/navigation_using_navigationagents.html

[smix8]

If I remember correct this was not a property at the beginning so the only way to set it was to call the function, but this is no longer the case, so could be changed.