Fix upgrade completion

We are using the call of updatectl --mark-update-successful to inform Apertis Update Manager about successful boot. Directive "Requires=" do not set the boot order, so it is possible what call of updatectl will be started before AUM and thus fail to mark update as successful. In case if such behavior repeated 3 times in a row the bootloader will rollback the system to previous state even for correctly updated device.

Set the dependency to AUM with "After=" directive in apertis-update-complete.service to force systemd to start AUM first.

PS I've catch this at least once.