cert-backup: fix invalid install for backends
There is no INSTALL_FILE but rather INSTALL_DATA.
Fix https://gitlab.labs.nic.cz/turris/turris-os-packages/issues/535
Self sign-up has been disabled due to increased spam activity. If you want to get access, please send an email to a project owner (preferred) or at gitlab(at)nic(dot)cz. We apologize for the inconvenience.
There is no INSTALL_FILE but rather INSTALL_DATA.
Fix https://gitlab.labs.nic.cz/turris/turris-os-packages/issues/535