The subject of the email is here in `email.js`, so we must wrap the string with `gettext` so it will be extracted during the `extract-pot` phase of L10n.

From a runtime perspective, the subject is put through gettext one more time that is strictly necissary, just like in Persona's `email.js`. If we sent 999 emails, then we would run this string through 1000 times. (999 plus startup).

The other option is to restructure where the subject line lives, diverging from Persona's email module.