Remove unused #postcodes action

This hasn’t been routable since b46d0b3a1c8146e9b1f52e26c3463025ac10e18e.
Reinstate old postcode view for civil courts
Remove unused @area_of_law instance variable from #civil action
Remove unused #civil_areas_of_law helper
Remove unused _local_authorities methods for civil areas of law
Merge pull request #226 from ministryofjustice/manage-civil-courts-by-postcode

Manage civil courts by postcode