Request for system-files for tube-converter

@soumyaDghosh system-files should not be required for access to such timezone files - these are generally provided by the base abstraction in AppArmor - I notice that zoneinfo-icu is missing from the base abstraction so I have filed a MR with the upstream AppArmor project to get this added. https://gitlab.com/apparmor/apparmor/-/merge_requests/1007 - if this does get merged then we can look at adding something similar to snapd so this is granted for all snaps.