Small bugfix in user import script.
Small bugfix in user import script.

In a past commit (8903c03e4b2e47a5776f6ff370ffa9a3a81959ab),
I changed the status code when creating a user from 201 from 200.
Unfortunately, I never updated the import user script.
...until now.

alphagov/digitalmarketplace-api,alphagov/digitalmarketplace-api,alphagov/digitalmarketplace-api