Document `optimize` parameter in `NavigationServer3D.map_get_path` and `NavigationServer2D.map_get_path`

[MajorMcDoom]

Your Godot version:

4.5.1.stable

Issue description:

The optimize parameter is undocumented in the class docs. It is only documented in the tutorial.

URL to the documentation page (if already existing):
https://docs.godotengine.org/en/stable/classes/class_navigationserver3d.html#class-navigationserver3d-method-map-get-path
https://docs.godotengine.org/en/stable/classes/class_navigationserver2d.html#class-navigationserver2d-method-map-get-path