Bump cachix/cachix-action from 15 to 16

Bumps [cachix/cachix-action](https://github.com/cachix/cachix-action) from 15 to 16.
- [Release notes](https://github.com/cachix/cachix-action/releases)
- [Commits](https://github.com/cachix/cachix-action/compare/v15...v16

)

---
updated-dependencies:
- dependency-name: cachix/cachix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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