Bump which from 4.1.0 to 4.2.1 (#315)

Bumps [which](https://github.com/harryfei/which-rs) from 4.1.0 to 4.2.1.
- [Release notes](https://github.com/harryfei/which-rs/releases)
- [Commits](https://github.com/harryfei/which-rs/compare/4.1.0...4.2.1

)

---
updated-dependencies:
- dependency-name: which
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

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