chore: release v4.0.0

[oxc-bot]

🤖 New release

• oxc_sourcemap: 3.0.2 -> 4.0.0 (⚠ API breaking changes)

⚠ oxc_sourcemap breaking changes

--- failure feature_missing: package feature removed or renamed ---

Description:
A feature has been removed from this package's Cargo.toml. This will break downstream crates which enable that feature.
        ref: https://doc.rust-lang.org/cargo/reference/semver.html#cargo-feature-remove
       impl: https://github.com/obi1kenobi/cargo-semver-checks/tree/v0.41.0/src/lints/feature_missing.ron

Failed in:
  feature rayon in the package's Cargo.toml

Changelog

4.0.0 - 2025-07-17

Other

• (deps) bump deps (#83)
• remove rayon feature (#81)

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This PR was generated with release-plz.