Remove email prefixes from doorkeeper titles

Summary: Fixes T10176. The prefix is not useful in the JIRA context, and doubtfully useful in Asana.

Test Plan: Load, make comment on revision, see link in JIRA is pretty.

Reviewers: Blessed Reviewers, epriestley

Reviewed By: Blessed Reviewers, epriestley

Subscribers: Korvin

Maniphest Tasks: T10176

Differential Revision: https://secure.phabricator.com/D15119