build(deps): bump nixpkgs-unstable from c6e5ca3 to d233902

Bumps [nixpkgs-unstable](https://github.com/NixOS/nixpkgs) from `c6e5ca3` to `d233902`.
- [Commits](NixOS/nixpkgs@c6e5ca3...d233902)

---
updated-dependencies:
- dependency-name: nixpkgs-unstable
  dependency-version: d233902339c02a9c334e7e593de68855ad26c4cb
  dependency-type: direct:production
...

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Author: dependabot[bot]