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