Correct the signature of mysqli_get_client_version()

[johnbillion]

The signature of mysqli_get_client_version() incorrectly includes a $link parameter which does not exist. The cause of this error is likely due to the documentation on php.net historically being incorrect.

• phpstan.org playground link, note the error on the PHP 7.1-7.4 tab
• PHP 7 source and PHP 5 source showing there is no parameter in this function
• Link to archive.org for php.net at PHP version 7 which incorrectly shows the parameter

As of PHP 8 the documentation on php.net is correct and the PHPStan stub for PHP 8 correctly shows no parameter.

[ondrejmirtes]

Thank you for the research!