build(deps): 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] <[email protected]>

.github/workflows/auto-update.yml

@@ -18,7 +18,7 @@ jobs:
           image: tonistiigi/binfmt:latest
           platforms: all
       - name: Install nix
-        uses: cachix/install-nix-action@V27
+        uses: cachix/install-nix-action@V28
         with:
           extra_nix_config: |
             experimental-features = nix-command flakes ca-derivations

.github/workflows/build.yml

@@ -42,7 +42,7 @@ jobs:
           platforms: all
 
       - name: Install nix
-        uses: cachix/install-nix-action@V27
+        uses: cachix/install-nix-action@V28
         with:
           nix_path: nixpkgs=channel:nixos-unstable
           extra_nix_config: |
@@ -106,7 +106,7 @@ jobs:
           image: tonistiigi/binfmt:latest
           platforms: all
       - name: Install nix
-        uses: cachix/install-nix-action@V27
+        uses: cachix/install-nix-action@V28
         with:
           nix_path: nixpkgs=channel:nixos-unstable
           extra_nix_config: |