Updates the requirements on [which](https://github.com/harryfei/which-rs) to permit the latest version.
- [Release notes](https://github.com/harryfei/which-rs/releases)
- [Commits](https://github.com/harryfei/which-rs/compare/3.1.0...4.0.1)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

• Commit b43b494
• Compare 6834f84..b43b494
• Branch master

Deyan Ginev