Summary: Fixes T1768. This is mostly a data cleanliness issue as duplicate rows don't really do anything, but let's clear it up now.
Test Plan: made some duplicate rows by adding the same auditor multiple times. ran ./bin/storage upgrade and it worked perfectly!
Reviewers: epriestley
Reviewed By: epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T1768
Differential Revision: https://secure.phabricator.com/D10849
