Support - Differential - fix rendering feed story where you removed a repository

Summary: Fixes T6176. Language here is a bit awkard but I wanted to use the verb "removed" *and* still have the object first, so I ended up adding the before details parenthetically.

Test Plan: story no longer fatal'd in my feed

Reviewers: epriestley, chad

Reviewed By: chad

Subscribers: epriestley, Korvin

Maniphest Tasks: T6176

Differential Revision: https://secure.phabricator.com/D10549