Touch up Badges emails

Summary: Ref T12270. Adds the name of the badge to the subject, fixes the double description.

Test Plan: Edit lots of badges with and without descriptions, see good emails.

Reviewers: epriestley

Reviewed By: epriestley

Subscribers: Korvin

Maniphest Tasks: T12270

Differential Revision: https://secure.phabricator.com/D17449