Bump tonic from 0.4.2 to 0.4.3 in /proto-compiler (informalsystems#886)

Bumps [tonic](https://github.com/hyperium/tonic) from 0.4.2 to 0.4.3.
- [Release notes](https://github.com/hyperium/tonic/releases)
- [Changelog](https://github.com/hyperium/tonic/blob/master/CHANGELOG.md)
- [Commits](hyperium/tonic@v0.4.2...v0.4.3)

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

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