Bump num-bigint from 0.4.1 to 0.4.2 (#68)

Bump num-bigint from 0.4.1 to 0.4.2 (#68)

Bumps [num-bigint](https://github.com/rust-num/num-bigint) from 0.4.1 to 0.4.2.
- [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/compare/num-bigint-0.4.1...num-bigint-0.4.2)

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

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