Update Diviner documentation to reference Phorge instead of Phabricator.
Summary: This commit also removes references to support pacts and updates links to point to the new upstream.
Test Plan: Generated Diviner documentation on a local install and verified that the changes look good.
Reviewers: O1 Blessed Committers, chris
Reviewed By: O1 Blessed Committers, chris
Subscribers: chris, speck, tobiaswiese
Maniphest Tasks: T15012
Differential Revision: https://we.phorge.it/D25007