We were previously using the set of `deviceToken`s returned by `rescindPushNotifs(...)` in `rescindAndUpdateBadgeCounts` to skip `updateBadgeCount(...)` for devices that had notifications rescinded. See D5606 for context.
Basically, we don't need the set of `deviceToken`s in `rescindAndUpdateBadgeCounts` and it isn't used anywhere else so it can be removed.