chore: bump orjson from 3.11.3 to 3.11.6 in /services/rag-backend

Bumps [orjson](https://github.com/ijl/orjson) from 3.11.3 to 3.11.6.
- [Release notes](https://github.com/ijl/orjson/releases)
- [Changelog](https://github.com/ijl/orjson/blob/master/CHANGELOG.md)
- [Commits](ijl/orjson@3.11.3...3.11.6)

---
updated-dependencies:
- dependency-name: orjson
  dependency-version: 3.11.6
  dependency-type: indirect
...

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Author: dependabot[bot]