Bump rmp-serde from 1.1.2 to 1.2.0

Bumps [rmp-serde](https://github.com/3Hren/msgpack-rust) from 1.1.2 to 1.2.0.
- [Release notes](https://github.com/3Hren/msgpack-rust/releases)
- [Commits](https://github.com/3Hren/msgpack-rust/commits/rmp-serde/v1.2.0)

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

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