PHP8 compatibility

[MelissaWu-SS]

There are two packages that this module requires, zendframework/zend-session and zendframework/zend-authentication are abandoned now, and they don't support php 8. But after investigation, it is found these two packages are not actually used by the SAML module. We can just remove these two packages from the composer.json of the SAML module.

Another package that the SAML module requires, onelogin/php-saml is in ^3.0.0, it should be upgraded to the latest version 4.1.0, which supports PHP 8 well.

Upgrade the phpunit version to ^9.5 for PHP 8 compatibility.

[satrun77]

Fixed thanks to @UndefinedOffset version 2.1.1 released