Update i18n doc about updating translations.
Update i18n doc about updating translations.

heartsucker/securedrop,conorsch/securedrop,conorsch/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,conorsch/securedrop,heartsucker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,ehartsuyker/securedrop,heartsucker/securedrop,conorsch/securedrop,conorsch/securedrop,heartsucker/securedrop