build: Bump zvariant from 5.5.3 to 5.6.0

Bumps [zvariant](https://github.com/dbus2/zbus) from 5.5.3 to 5.6.0.
- [Release notes](https://github.com/dbus2/zbus/releases)
- [Commits](https://github.com/dbus2/zbus/compare/zvariant-5.5.3...zvariant-5.6.0)

---
updated-dependencies:
- dependency-name: zvariant
  dependency-version: 5.6.0
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Cargo.lock

@@ -2957,9 +2957,9 @@ dependencies = [
 
 [[package]]
 name = "zvariant"
-version = "5.5.3"
+version = "5.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9d30786f75e393ee63a21de4f9074d4c038d52c5b1bb4471f955db249f9dffb1"
+checksum = "d91b3680bb339216abd84714172b5138a4edac677e641ef17e1d8cb1b3ca6e6f"
 dependencies = [
  "endi",
  "enumflags2",
@@ -2971,9 +2971,9 @@ dependencies = [
 
 [[package]]
 name = "zvariant_derive"
-version = "5.5.3"
+version = "5.6.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "75fda702cd42d735ccd48117b1630432219c0e9616bf6cb0f8350844ee4d9580"
+checksum = "3a8c68501be459a8dbfffbe5d792acdd23b4959940fc87785fb013b32edbc208"
 dependencies = [
  "proc-macro-crate",
  "proc-macro2",