Bump cachix/install-nix-action from V27 to 28

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from V27 to 28. This release includes the previously tagged commit.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@V27...V28)

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

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

.github/workflows/CI.yml

@@ -152,7 +152,7 @@ jobs:
       - name: Checkout
         uses: actions/checkout@v4
       - name: Install nix
-        uses: cachix/install-nix-action@V27
+        uses: cachix/install-nix-action@V28
         with:
           nix_path: nixpkgs=channel:nixos-unstable
       - name: Install dependencies