[php-src] Issue #8446: new Collator(null) should not trigger a deprecation warning

Issue: https://github.com/php/php-src/issues/8446 Author: claudepache ### Description The following code: ```php <?php new Collator(null); ``` Resulted in this output: ``` Deprecated: Collator::__construct(): Passing null to parameter #1 ($locale) of type string is deprecated in /in/AUfEa on line 2 ``` However, [the documentation says](https://www.php.net/manual/en/collator.construct.php): “if null is passed for the locale, the default locale's collation rules will be used”. Therefore, I expect that the $locale parameter is nullable, and no deprecation warning is triggered. (Alternatively, in case "" has the same effect of what is currently documented for null, the documentation may be amended.) ### PHP Version PHP 8.1.5 ### Operating System _No response_