build(deps): bump nixpkgs-master from 118ca19 to ef661c0

Bumps [nixpkgs-master](https://github.com/NixOS/nixpkgs) from `118ca19` to `ef661c0`.
- [Commits](NixOS/nixpkgs@118ca19...ef661c0)

---
updated-dependencies:
- dependency-name: nixpkgs-master
  dependency-version: ef661c0bdf3e5b1c7cd8871fd72ab128a13286b0
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]