Don't show any "2FA required" message if it's not actually required

Prior, if the user had enabled and then disabled 2FA, they would be
shown a "You must enable Two-factor Authentication for your account."
message when going back to re-activate it, even if 2FA enforcement was
disabled.

app/controllers/profiles/two_factor_auths_controller.rb

@@ -12,12 +12,14 @@ class Profiles::TwoFactorAuthsController < Profiles::ApplicationController
 
     current_user.save! if current_user.changed?
 
+    if two_factor_authentication_required?
       if two_factor_grace_period_expired?
         flash.now[:alert] = 'You must enable Two-factor Authentication for your account.'
       else
         grace_period_deadline = current_user.otp_grace_period_started_at + two_factor_grace_period.hours
         flash.now[:alert] = "You must enable Two-factor Authentication for your account before #{l(grace_period_deadline)}."
       end
+    end
 
     @qr_code = build_qr_code
   end