update zbus dependency

libslirp-rs is currently one of the last three packages in Fedora that depends on zbus v1. This version is increasingly outdated and obsolete - Fedora ships packages for zbus v1 and v4, and upstream released v5 this week.

zbus v1 pulls in lots of other old crate versions and / or obsolete crates. Please port this project to v4 or v5. I plan to retire zbus v1 from Fedora 42+ within a few months.