Add a lint error about use of PHP short array syntax ('[...]')

Summary: Ref T11409. Add lint to detect using [...] to define arrays. This doesn't work in PHP 5.2/5.3, which some of our users run.

Test Plan:

• Ran arc unit.
• Ran arc lint src/applications/harbormaster/conduit/HarbormasterQueryBuildsConduitAPIMethod.php to detect the issue in T11409.

Reviewers: yelirekim, chad

Reviewed By: chad

Maniphest Tasks: T11409

Differential Revision: https://secure.phabricator.com/D16357