Update test mail setup for Spree 2
Update test mail setup for Spree 2

https://github.com/openfoodfoundation/openfoodnetwork/issues/2882

The email setup differs between Spree 1 and Spree 2. We already
encapsulated that setup in a single method which now needed changing.

lin-d-hop/openfoodnetwork,lin-d-hop/openfoodnetwork,Matt-Yorkley/openfoodnetwork,Matt-Yorkley/openfoodnetwork,lin-d-hop/openfoodnetwork,mkllnk/openfoodnetwork,openfoodfoundation/openfoodnetwork,openfoodfoundation/openfoodnetwork,mkllnk/openfoodnetwork,openfoodfoundation/openfoodnetwork,openfoodfoundation/openfoodnetwork,Matt-Yorkley/openfoodnetwork,lin-d-hop/openfoodnetwork,mkllnk/openfoodnetwork,mkllnk/openfoodnetwork,Matt-Yorkley/openfoodnetwork