It's removed because INDI FLI driver no longer requires it, it uses libusb now. Make sure to run sudo apt-get dist-upgrade to get everything and restart your PC.
Thank you for the explanation!
Nevertheless, where could I download these two binary packages?
fliusb-dkms-1.3+r3810~201802271457~ubuntu16.04.1
fliusb-source-1.3+r3810~201802271457~ubuntu16.04.1
If I am not wrong these are the latest version available.
I will need them for my client software which uses INDI Library.