fix(generator): update rust crate which to v6 - autoclosed

[renovate[bot]]

This PR contains the following updates:

Package	Type	Update	Change
which	build-dependencies	major	4.4 -> 6.0

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Release Notes

harryfei/which-rs (which)

### [`v6.0.0`](https://togithub.com/harryfei/which-rs/blob/HEAD/CHANGELOG.md#600) [Compare Source](https://togithub.com/harryfei/which-rs/compare/5.0.0...6.0.0) - MSRV is now 1.70 - Upgraded all dependencies to latest version ### [`v5.0.0`](https://togithub.com/harryfei/which-rs/blob/HEAD/CHANGELOG.md#500) [Compare Source](https://togithub.com/harryfei/which-rs/compare/4.4.2...5.0.0) - Remove several unused error messages - Windows executables can now be found even if they don't have a '.exe' extension. - Add new error message, `Error::CannotGetCurrentDirAndPathListEmpty`

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Configuration

📅 Schedule: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined).

🚦 Automerge: Disabled by config. Please merge this manually once you are satisfied.

♻ Rebasing: Whenever PR becomes conflicted, or you tick the rebase/retry checkbox.

🔕 Ignore: Close this PR and you won't be reminded about this update again.

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• [ ] If you want to rebase/retry this PR, check this box

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This PR has been generated by Mend Renovate. View repository job log here.

[renovate[bot]]

⚠ Artifact update problem

Renovate failed to update an artifact related to this branch. You probably do not want to merge this PR as-is.

♻ Renovate will retry this branch, including artifacts, only when one of the following happens:

• any of the package files in this branch needs updating, or
• the branch becomes conflicted, or
• you click the rebase/retry checkbox if found above, or
• you rename this PR's title to start with "rebase!" to trigger it manually

The artifact failure details are included below:

File name: generator/Cargo.lock

Command failed: cargo update --config net.git-fetch-with-cli=true --manifest-path generator/Cargo.toml --package which@4.4.2 --precise 6.0.0
    Updating crates.io index
error: failed to select a version for the requirement `which = "^4.2.1"`
candidate versions found which didn't match: 6.0.0
location searched: crates.io index
required by package `bindgen v0.69.0`
    ... which satisfies dependency `bindgen = "^0.69"` (locked to 0.69.0) of package `libvips-bindings v0.0.2 (/tmp/renovate/repos/github/olxgroup-oss/libvips-rust-bindings/generator)`
perhaps a crate was updated and forgotten to be re-vendored?