build(deps): bump fenix from 6012e54 to 2eff81f

Bumps [fenix](https://github.com/nix-community/fenix) from `6012e54` to `2eff81f`.
- [Commits](nix-community/fenix@6012e54...2eff81f)

---
updated-dependencies:
- dependency-name: fenix
  dependency-version: 2eff81fc84390a35e1565395ae945d9394856824
  dependency-type: direct:production
...

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Author: dependabot[bot]