Check if user can create project before showing shortcut

Summary: In Maniphest, we provide an additional caption shortcut if you can create projects, which has no use if you cant. Fixes T6969

Test Plan: Check page with and without a user's capability.

Reviewers: btrahan, epriestley

Reviewed By: epriestley

Subscribers: Korvin, epriestley

Maniphest Tasks: T6969

Differential Revision: https://secure.phabricator.com/D11390