Rename "final_model()" to "finalize_model()"

In the English language, "final" is an adjective, not a predicate. The name "final model" therefore sounds like a thing, not an action.
So I'd propose to rename the function (and keep a redirect for compatibility) to "finalize_model".

This change would help newcomers, especially from an English background.

Of course, all documentation would need to be updated as well.