Remove metamta.send-immediately
Summary:
Ref T3857.
- Always send mail via daemons. This lets us get rid of this config, and is generally much more performant.
- After D7964, we warn if daemons aren't running.
Test Plan: Sent some mail.
Reviewers: btrahan
Reviewed By: btrahan
CC: aran
Maniphest Tasks: T3857
Differential Revision: https://secure.phabricator.com/D7965