Update which requirement from 4 to 5

Updates the requirements on [which](https://github.com/harryfei/which-rs) to permit the latest version.
- [Changelog](https://github.com/harryfei/which-rs/blob/master/CHANGELOG.md)
- [Commits](https://github.com/harryfei/which-rs/commits)

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

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

bindings-generator/Cargo.toml

@@ -25,4 +25,4 @@ regex = { version = "1.5.5", default-features = false, features = ["std", "unico
 roxmltree = "0.18"
 syn = { version = "1", features = ["full", "extra-traits", "visit"] }
 unindent = "0.2.0"
-which = { optional = true, version = "4" }
+which = { optional = true, version = "5" }