Add password challenge to 2FA settings, e-mail notifications (#11878)

Fix #3961

config/locales/simple_form.en.yml

@@ -43,6 +43,8 @@ en:
         domain: This domain will be able to fetch data from this server and incoming data from it will be processed and stored
       featured_tag:
         name: 'You might want to use one of these:'
+      form_challenge:
+        current_password: You are entering a secure area
       imports:
         data: CSV file exported from another Mastodon server
       invite_request: