Turn off captive observations by default in the app

Added an issue for Android here and reminded Alex about it now that 3.0 is out, although part of me wonders if it might backfire in situations where a user observes common garden plants and they don’t see any nearby on the map. However, in my experience those users are often not looking at range maps for suggested IDs.

EDIT: whoops, looks like it’s working in iOS 3.0, at least in default view. If you tap on the map, you’ll see the casual obs.