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

@@ -12,11 +12,13 @@ class Profiles::TwoFactorAuthsController < Profiles::ApplicationController
 
     current_user.save! if current_user.changed?
 
-    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)}."
+    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