Fix workboard link from project profile pages

Summary: Fixes T5165. This uses `$this->id`, but that may not always be populated anymore. Use the project ID directly instead.

Test Plan: Clicked a workboard link.

Reviewers: btrahan, chad

Reviewed By: chad

Subscribers: epriestley

Maniphest Tasks: T5165

Differential Revision: https://secure.phabricator.com/D9266