ubiquity-frontend-kde: the secure boot configurations are not in the disabled state when "installing third-party drivers" is unselected

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Steps to reproduce:

1. Enable secure boot;
2. Open ubiquity kde_ui and go to next screen after the keyboard one.

Observed behavior:
The third-party drivers checkbox is unselected and the secure boot configuration is not disabled like in ubiquity-frontend-gtk, suggesting that secure boot should be configured even if the third-party drivers option is disabled. I tested here and configured the secure boot without checking the drivers option and ubiquity didn't show any warning.