Missing line in tutorial about navigation with different actors

[1998marcom]

Godot version: 4.0.2

Issue description: Supposedly missing line in tutorial about navigation with different actors (and typo)

URL to the documentation page: docs.godotengine.org/en/4.0/tutorials/navigation/navigation_different_actor_types.html

The page has some good code for bootstrapping one's own code, but I had issues with regions not merging until I manually activated the navigation maps with NavigationServer3D.map_set_active(map_rid, true). If the maps are inactive by default and require manual activation, and this is their intended behaviour, I would add the previous line to the tutorial.

Also, the penultimate line should be:
var path_small_agent = NavigationServer3D.map_get_path(navigation_map_small, start_pos, end_pos, true)
rather than:
var path_small_agent = NavigationServer3D.map_get_path(navigation_mesh_small_size, start_pos, end_pos, true)
I believe it is just a clear typo.