nix: bump the nix group with 2 updates (#25)

Bumps the nix group with 2 updates: [cabal-src](https://github.com/haskell/cabal) and [ghc-src](https://github.com/ghc/ghc).


Updates `cabal-src` from `46188fa` to `fa68585`
- [Release notes](https://github.com/haskell/cabal/releases)
- [Commits](haskell/cabal@46188fa...fa68585)

Updates `ghc-src` from `f6f2343` to `d415f38`
- [Commits](ghc/ghc@f6f2343...d415f38)

---
updated-dependencies:
- dependency-name: cabal-src
  dependency-version: fa68585d698f28b0f4bc18e810c27a8e659f5012
  dependency-type: direct:production
  dependency-group: nix
- dependency-name: ghc-src
  dependency-version: d415f38a75cc88921a344220ad2eed0e82fdb5ff
  dependency-type: direct:production
  dependency-group: nix
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: dependabot[bot]