gpgolconfig: Remove superfluous checks for enabled or checked groups

The child widgets of a group box are implicitly forced disabled if the
group box is disabled or not checked. Moreover, child widgets which were
explicitly disabled are not enabled if a group box is checked. Hence,
it's superfluous to check the state of group boxes explicitly and to
react on a group box being toggled.

• GnuPG-bug-id: T8254