build(deps): bump serial_test from 0.8.0 to 0.9.0 (#745)

Bumps [serial_test](https://github.com/palfrey/serial_test) from 0.8.0 to 0.9.0.
- [Release notes](https://github.com/palfrey/serial_test/releases)
- [Commits](palfrey/serial_test@v0.8.0...v0.9.0)

---
updated-dependencies:
- dependency-name: serial_test
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>