Update hex requirement from 0.3 to 0.4 (#13)
Update hex requirement from 0.3 to 0.4 (#13)

Updates the requirements on [hex](https://github.com/KokaKiwi/rust-hex) to permit the latest version.
- [Release notes](https://github.com/KokaKiwi/rust-hex/releases)
- [Commits](https://github.com/KokaKiwi/rust-hex/compare/v0.3.0...v0.4.0)

Signed-off-by: dependabot-preview[bot] <5bdcd3c0d4d24ae3e71b3b452a024c6324c7e4bb@dependabot.com>
malept/crypto-hash,malept/crypto-hash