enabled short array notation in CS

.php_cs.dist

@@ -10,6 +10,7 @@ return PhpCsFixer\Config::create()
         '@Symfony:risky' => true,
         '@PHPUnit48Migration:risky' => true,
         'php_unit_no_expectation_annotation' => false, // part of `PHPUnitXYMigration:risky` ruleset, to be enabled when PHPUnit 4.x support will be dropped, as we don't want to rewrite exceptions handling twice
+        'array_syntax' => array('syntax' => 'short'),
         'fopen_flags' => false,
         'ordered_imports' => true,
         'protected_to_private' => false,