[php-src] Issue #20384: Confirm if ob_gzhandler is impacted by ob_start handler changes

Issue: https://github.com/php/php-src/issues/20384 Author: andrewnicols ### Description I'm just trying to confirm whether ob_gzhandler() is impacted by #18932. ob_gzhandler() is [documented](https://www.php.net/manual/en/function.ob-gzhandler.php) to return string|false, and I cannot see any recent changes in ext/zlib/zlib.c which modify the handler to not return false in the case where the browser does not support gzip. However in the testing I have tried to do, I am unable to trigger any deprecation notice. It would be good to confirm, and document, that this method is safe to use with ob_start(). ### PHP Version ```plain 8.5 ``` ### Operating System _No response_