build(deps): bump cachix/install-nix-action in /.github/workflows

Bumps [cachix/install-nix-action](https://github.com/cachix/install-nix-action) from 29 to 30.
- [Release notes](https://github.com/cachix/install-nix-action/releases)
- [Commits](cachix/install-nix-action@v29...v30)

---
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/check-nixos-config.yaml

@@ -7,7 +7,7 @@ jobs:
     steps:
       - uses: actions/checkout@v4
       - name: Install Nix
-        uses: cachix/install-nix-action@v29
+        uses: cachix/install-nix-action@v30
         with:
           extra_nix_config: |
             experimental-features = nix-command flakes