Remove "metamta.precedence-bulk" option (always enable it)
Summary: Ref T7746. This might possibly improve deliverability. Or might make it worse. Who knows?
Test Plan: grep
Reviewers: btrahan
Reviewed By: btrahan
Subscribers: epriestley
Maniphest Tasks: T7746
Differential Revision: https://secure.phabricator.com/D12266