Bump cachix/install-nix-action from V28 to 29 (#203)

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from V28 to 29. This release includes the previously tagged commit.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@V28...v29)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
...

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

.github/workflows/nix.yml

@@ -12,7 +12,7 @@ jobs:
  runs-on: ubuntu-latest
  steps:
  - uses: actions/checkout@v4
- - uses: cachix/install-nix-action@V28
+ - uses: cachix/install-nix-action@v29
  with:
  nix_path: nixpkgs=channel:nixos-unstable
  - uses: DeterminateSystems/magic-nix-cache-action@v8