Revert "Change default keyboard interactivity from exclusive to none"

This reverts commit be637838.

It broke keyboard input in sddm greeter. While defaulting to a non-spec
value is not great, it's also not that critical. It might be worth
considering synchronizing Qt::WindowDoesNotAcceptFocus with the keyboard
interactivity flag, but the tricky part is that the keyboard interactivty
is not just a boolean.

BUG: 477251