Bump cachix/install-nix-action from V27 to 28 (#889)

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
...

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.github/workflows/ci.yml

@@ -33,7 +33,7 @@ jobs:
           components: rustfmt
           profile: minimal
           toolchain: nightly
-      - uses: cachix/install-nix-action@V27
+      - uses: cachix/install-nix-action@V28
         if: ${{ matrix.os != 'windows-latest' }}
         with:
           nix_path: nixpkgs=channel:nixos-unstable