R1:eeef60a67867

Update "bin/policy show" to use PolicyCodex

Summary: Fixes T12541. `describeAutomaticCapability()` is no longer required to implement `PolicyInterface`. Use PolicyCodex instead.

Test Plan: {F4889642}

Reviewers: chad

Reviewed By: chad

Maniphest Tasks: T12541

Differential Revision: https://secure.phabricator.com/D17658