Issue #3508173 by dydave: Fixed GitLab CI configuration causing jobs to fail...

https://www.drupal.org/project/admin_toolbar/issues/3508173

1 - Fixed GitLab CI configuration causing jobs to fail:

For more details, see issue: Help fixing jobs for Admin Toolbar

2 - Fixed broken PHPUnit tests for D11:

Adjusted AdminToolbarSettingsFormTest to be compatible with D11 by modifying a check with xpath:

• from: li node contains a node and not ul
• to: li node has exactly one child which is an a link tag.