Update CS fixer config

Author: mbabker

.php-cs-fixer.php

@@ -13,7 +13,7 @@
         'fopen_flags' => false,
         'linebreak_after_opening_tag' => false,
         'no_superfluous_phpdoc_tags' => ['remove_inheritdoc' => true],
-        'nullable_type_declaration_for_default_null_value' => ['use_nullable_type_declaration' => true],
+        'nullable_type_declaration_for_default_null_value' => true,
         'single_line_empty_body' => true,
     ])
     ->setRiskyAllowed(true)