Do not request confirmation by default for private space unlocks

Fix face unlock confirmation button behavior to respect "always
require confirmation" setting. Adjust the description of the
confirmation toggle in private space face unlock settings to
reflect this change.
Screenshot: https://screenshot.googleplex.com/4uHfm9Z3ZE56ZaT.png

Bug: 342383195
Test: Tested manually by flashing local build
Change-Id: I0f742839a862fe66cacad9f5704dbe8b0df3a0c2