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...6.0.0)

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

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

bindings-generator/Cargo.toml

@@ -25,4 +25,4 @@ regex = { version = "1.5.5", default-features = false, features = ["std", "unico
 roxmltree = "0.19"
 syn = { version = "1", features = ["full", "extra-traits", "visit"] }
 unindent = "0.2.0"
-which = { optional = true, version = "5" }
+which = { optional = true, version = "6" }