chore: update prost-build requirement from 0.12 to 0.13 in /rust (#336)

Updates the requirements on [prost-build](https://github.com/tokio-rs/prost) to permit the latest version.
- [Release notes](https://github.com/tokio-rs/prost/releases)
- [Changelog](https://github.com/tokio-rs/prost/blob/master/CHANGELOG.md)
- [Commits](tokio-rs/prost@v0.12.0...v0.13.0)

---
updated-dependencies:
- dependency-name: prost-build
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Carlos Rodriguez <carlos@interchain.io>

rust/codegen/Cargo.toml

@@ -9,5 +9,5 @@ edition = "2018"
 [dependencies]
 bytes = "1.0.1"
 prost = "0.13"
-prost-build = "0.12"
+prost-build = "0.13"
 informalsystems-pbjson-build = "0.7.0"