Minor fix for the ArcanistXHPASTLinter.

Summary: This LINT_PHP_53_FEATURES should have been replaced with LINT_PHP_COMPATIBILITY in D9576.

Test Plan: Ran arc unit.

Reviewers: epriestley, Blessed Reviewers

Reviewed By: epriestley, Blessed Reviewers

Subscribers: epriestley, Korvin

Differential Revision: https://secure.phabricator.com/D9655