Improve linter handling of short array syntax
Summary: Currently, linting PHP short array syntax (i.e. [...]) throws an exception ("Expected open parentheses"). This diff relaxes some restrictions which prevent short array syntax from linting with ArcanistParenthesesSpacingXHPASTLinterRule.
Test Plan: Modified test cases.
Reviewers: epriestley, Blessed Reviewers
Reviewed By: epriestley, Blessed Reviewers
Subscribers: agenticarus, Korvin
Differential Revision: https://secure.phabricator.com/D13895