Add "voucher:" before voucher code on order confirmation emails

[RachL]

Description

- As a: shopper
- On page: order confirmation email
- I want to be able to do:

I see voucher codes on order confirmation email but it might not be super clear. The goal here is to do the same as on the order confirmation page and add "voucher:" before the vouche code

Here is what we have currently in an email using "BADABOOM" as voucher code

And here is the current order confirmation page:

Acceptance Criteria & Tests

1. Login as enterprise manager
2. Set up a voucher in Enterprise settings > Vouchers
3. Use this voucher in an order as a shopper
4. See that confirmation email contains the text "voucher:" before the voucher code
5. Check this text can be translated