Fix getpriority test with negative return value

Negative return values are valid and denote higher priority.

https://man7.org/linux/man-pages/man2/setpriority.2.html

Author: iluuu1994

ext/pcntl/tests/pcntl_getpriority_basic.phpt

@@ -16,4 +16,4 @@ if (!function_exists('pcntl_getpriority')) {
 var_dump(pcntl_getpriority());
 ?>
 --EXPECTF--
-int(%d)
+int(%i)