R1:7492eb36d4fe

Fix missing label in Request Review

Summary: Fixes T3564. This was a change out of FB recently, see D6340. Add a missing label.

Test Plan: "Request Review" now has a label.

Reviewers: chad

Reviewed By: chad

CC: aran

Maniphest Tasks: T3564

Differential Revision: https://secure.phabricator.com/D6484