Escalate missing error when :raise is true

Before ec16ba75a5493b9da972eea08bae630eba35b62f,
ActionView::Helpers::TranslationHelper#translate has raised errors with
specifying options[:raise] to true.

This should work by this fix:

     begin
       t(:"translations.missing", raise: true)
     rescue I18n::MissingTranslationData
       p :hello!
     end