build(deps): bump cachix/install-nix-action from V27 to 28 (#623)

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](https://github.com/cachix/install-nix-action/compare/V27...V28)

---
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/test.yml

@@ -11,7 +11,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
     - uses: actions/checkout@v4
-    - uses: cachix/install-nix-action@V27
+    - uses: cachix/install-nix-action@V28
     - name: Add keys group (needed for go tests)
       run: sudo groupadd keys
     - name: Run unit tests

.github/workflows/update-vendor-hash.yml

@@ -14,7 +14,7 @@ jobs:
           ref: ${{ github.event.pull_request.head.sha }}
           fetch-depth: 0
       - name: Install Nix
-        uses: cachix/install-nix-action@V27
+        uses: cachix/install-nix-action@V28
         with:
           github_access_token: ${{ secrets.GITHUB_TOKEN }}
           nix_path: nixpkgs=channel:nixos-unstable

.github/workflows/upgrade-flakes.yml

@@ -10,7 +10,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Install Nix
-        uses: cachix/install-nix-action@V27
+        uses: cachix/install-nix-action@V28
         with:
           extra_nix_config: |
             access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}