build(deps): bump cachix/install-nix-action

Bumps the gha-version-updates group with 1 update: [cachix/install-nix-action](https://github.com/cachix/install-nix-action).


Updates `cachix/install-nix-action` from 27 to 29
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](https://github.com/cachix/install-nix-action/compare/v27...v29)

---
updated-dependencies:
- dependency-name: cachix/install-nix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: gha-version-updates
...

Signed-off-by: dependabot[bot] <support@github.com>

.github/workflows/CI.yml

@@ -32,7 +32,7 @@ jobs:
     - name: Checkout
       uses: actions/checkout@v4
     - name: "Install Nix"
-      uses: cachix/install-nix-action@v27
+      uses: cachix/install-nix-action@v29
       with:
         install_url: https://releases.nixos.org/nix/nix-2.18.4/install
     - name: "Set Up Binary Cache"