Ensure a message about invalid scope reaches the user if trying to vote on a wrong scope

[deivid-rodriguez]

For now, I'm removing the unused i18n key in ad98dfd.

However, I'm not sure about this one. We should definitely protect against this at the controller level but will there be an expected user flow that results in this? In the case of protecting at the controller level, I'm not sure we should give such a specific message to the user. 🤔