Bump cachix/install-nix-action from 27 to 28

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 27 to 28.
- [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
  update-type: version-update:semver-major
...

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

.github/workflows/cachix.yml

@@ -35,7 +35,7 @@ jobs:
         with:
           ref: ${{ inputs.ref }}
       - name: Install Nix
-        uses: cachix/install-nix-action@v27
+        uses: cachix/install-nix-action@V28
         with:
           github_access_token: '${{ secrets.GITHUB_TOKEN }}'
       - name: Enable Cachix