3491: Require SelectPhoneFormMapper in phone controller.
3491: Require SelectPhoneFormMapper in phone controller.

Followup needed to ensure removing this line will fail tests on the
command line.

Authors: 78ba85360bda86c19bfe5404debc7fa7b36f8e68@oswaldquek

alphagov/verify-frontend,alphagov/verify-frontend,alphagov/verify-frontend,alphagov/verify-frontend