Fix array_flip() on PHP 8.1 (#673)

Author: cedric-anne

generated/8.1/functionsList.php

@@ -9,6 +9,7 @@
 return [
     'array_all', // false is not an error
     'array_combine', // this function throws an error instead of returning false since PHP 8.0
+    'array_flip', // always return an array since PHP 8.0, see https://github.com/php/doc-en/issues/1178
     'array_walk_recursive', // actually returns always true, see https://github.com/php/doc-en/commit/cec5275f23d2db648df30a5702b378044431be97
     'date', // this function throws an error instead of returning false PHP 8.0, but the doc has only been updated since PHP 8.4
     'getallheaders', // always return an array since PHP 7, see https://github.com/php/doc-en/commit/68e52ef14de33f6752a8fdda1ae83c861c5babdb