build(deps): update thiserror requirement in /flipt-engine-ffi (#518)

Updates the requirements on [thiserror](https://github.com/dtolnay/thiserror) to permit the latest version.
- [Release notes](https://github.com/dtolnay/thiserror/releases)
- [Commits](dtolnay/thiserror@1.0.63...2.0.3)

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

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

flipt-engine-ffi/Cargo.toml

@@ -18,7 +18,7 @@ tokio-util = { version = "0.7", features = ["io", "codec"] }
 futures-util = "0.3.30"
 native-tls = { version = "0.2", features = ["vendored"] }
 futures = "0.3"
-thiserror = "1.0.63"
+thiserror = "2.0.3"
 reqwest-retry = "0.6.1"
 reqwest-middleware = "0.3.3"