Bump num-bigint from 0.4.5 to 0.4.6 (informalsystems#4076)

Bumps [num-bigint](https://github.com/rust-num/num-bigint) from 0.4.5 to 0.4.6.
- [Changelog](https://github.com/rust-num/num-bigint/blob/master/RELEASES.md)
- [Commits](rust-num/num-bigint@num-bigint-0.4.5...num-bigint-0.4.6)

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

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