Update libksane and Skanlite build dependencies

Motivated by the newly added dependency on KSaneCore by libksane.

However, this does currently nothing with kdesrc-build as there is a module-set definition presumably overriding the listed dependencies at https://invent.kde.org/sdk/kdesrc-build/-/blob/master/kf5-applications-build-include#L43

My knowledge of kdesrc-build is quite limited, so I don't know what this is supposed to do and what is the right way to handle this...