Remove "arcanist projects" from Releeph
Summary: Ref T7604. Remove arcanist projects from #releeph.
Test Plan: I don't really know how to use Releeph but I clicked around and nothing seemed too broken.
Reviewers: #blessed_reviewers, epriestley
Reviewed By: #blessed_reviewers, epriestley
Subscribers: Korvin, epriestley
Maniphest Tasks: T7604
Differential Revision: https://secure.phabricator.com/D12898