R1:daadf955378c

Fix visibility of `PhutilArgumentWorkflow::didConstruct` methods

Summary: Ref T6822.

Test Plan: `grep`. This method is only called from within `PhutilArgumentWorkflow::__construct`.

Reviewers: epriestley, #blessed_reviewers

Reviewed By: epriestley, #blessed_reviewers

Subscribers: Korvin, epriestley

Maniphest Tasks: T6822

Differential Revision: https://secure.phabricator.com/D11415