fix(settings): Notify instead of flash when user updates his emai

Closes #16861

server/boot/settings.js

@@ -43,7 +43,7 @@ export default function settingsController(app) {
     const { user, body: { email } } = req;
     return user.requestUpdateEmail(email)
       .subscribe(
-        message => res.sendFlash(alertTypes.info, message),
+        message => res.json({ message }),
         next
       );
   }