build: Bump zvariant from 5.6.0 to 5.7.0

Bumps [zvariant](https://github.com/dbus2/zbus) from 5.6.0 to 5.7.0.
- [Release notes](https://github.com/dbus2/zbus/releases)
- [Commits](z-galaxy/zbus@zvariant-5.6.0...zvariant-5.7.0)

---
updated-dependencies:
- dependency-name: zvariant
  dependency-version: 5.7.0
  dependency-type: indirect
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]