build(deps): update zbus requirement from 3.6 to 4.2 in /ladspa

Updates the requirements on [zbus](https://github.com/dbus2/zbus) to permit the latest version.
- [Release notes](https://github.com/dbus2/zbus/releases)
- [Commits](dbus2/zbus@zbus-3.6.0...zbus-4.2.0)

---
updated-dependencies:
- dependency-name: zbus
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

ladspa/Cargo.toml

@@ -24,5 +24,5 @@ ndarray = "^0.15"
 env_logger = "0.10"
 uuid = { version = "1.2.1", features = ["v4", "fast-rng"] }
 log = { version = "0.4", features = ["std"] }
-zbus = { version = "3.6", optional = true }
+zbus = { version = "4.2", optional = true }
 event-listener = { version = "2.5", optional = true }