[native] Enable NUX

Summary:
Turn on NUX for everyone.

https://linear.app/comm/issue/ENG-9111/remove-the-flag-once-we-are-ready-to-launch-nux

Test Plan: Delete the app, create a new account on iOS simulator, and check if the NUX was shown.

Reviewers: kamil, will

Reviewed By: kamil

Subscribers: ashoat

Differential Revision: https://phab.comm.dev/D13422