Callback after_config in auth_saml2 component should be migrated to new hook callback for core\hook\after_config

[mbullie]

Callback after_config in auth_saml2 component should be migrated to new hook callback for core\hook\after_config line 7216 of \lib\moodlelib.php: call to debugging() line 7330 of \lib\moodlelib.php: call to {closure}() line 36 of \lib\classes\hook\after_config.php: call to get_plugins_with_function() line 1198 of \lib\setup.php: call to core\hook\after_config->process_legacy_callbacks() line 27 of \config.php: call to require_once() line 87 of \admin\index.php: call to require()

[dravek]

Hi, I created this PR https://github.com/catalyst/moodle-auth_saml2/pull/839 to fix the issue. Cheers!