Update which requirement from 5 to 6

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)
- [Changelog](https://github.com/harryfei/which-rs/blob/master/CHANGELOG.md)
- [Commits](harryfei/which-rs@5.0.0...5.0.0)

---
updated-dependencies:
- dependency-name: which
  dependency-type: direct:production
...

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

Cargo.toml

@@ -40,7 +40,7 @@ thiserror = "1"
 tokio = "1"
 toml = "0.8"
 walkdir = "2"
-which = "5"
+which = "6"
 zeroize = { version = "1.7" }
 
 [patch.crates-io]