Bug 15101: Don't display sys pref AllowPkiAuth under CAS heading

 Bug 15101: Don't display sys pref AllowPkiAuth under CAS heading

The system preference AllowPkiAuth display under the heading
CAS authentication, but is actually a separate authentication
option. Patch creates a separate heading for it.

To test:
- Go to Administration > System preferences > Tab Administration
- Verify that AllowPkiAuth is now displayed separately

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Brendan A Gallagher <brendan@bywatersolutions.com>