mavlink: 1.0.9-8 in 'hydro/distribution.yaml' [bloom]

Increasing version of package(s) in repository `mavlink` to `1.0.9-8`:

- upstream repository: https://github.com/mavlink/mavlink.git
- release repository: https://github.com/vooon/mavlink-gbp-release.git
- distro file: `hydro/distribution.yaml`
- bloom version: `0.5.11`
- previous version for package: `1.0.9-7`