Refactor the application model
Refactor the application model

When the personal_information model was split out, the age
validation code was moved over, along with the tests.

The original code was left behind and is no longer used.

This removal should improve the code-climate score for the
(decreasingly) monolithic application model.

ministryofjustice/fr-staffapp,ministryofjustice/fr-staffapp,ministryofjustice/fr-staffapp,ministryofjustice/fr-staffapp