Remove obsolete fields from API business response

The `business.arMaxDate` and `business.arMinDate` fields are not used by the UI, so they can be deleted from the business endpoint response. (The UI instead uses the data from the AR filing meta.)

Note that the API may still want to calculate these values to validate the Annual Report dates when an AR is filed.

Start by locating the business endpoint response and the code that validates Annual Report dates when an AR is filed. Trace how business.arMaxDate and business.arMinDate are assembled, then check the relevant API tests if present. Done means the response omits both fields while Annual Report date validation still works.

Written by the indexing model from the issue text.