rust: bump num-bigint from 0.4.2 to 0.4.3

Bumps [num-bigint](https://github.com/rust-num/num-bigint) from 0.4.2 to 0.4.3.
- [Release notes](https://github.com/rust-num/num-bigint/releases)
- [Changelog](https://github.com/rust-num/num-bigint/blob/master/RELEASES.md)
- [Commits](https://github.com/rust-num/num-bigint/commits)

---
updated-dependencies:
- dependency-name: num-bigint
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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