Bump cachix/install-nix-action from 29 to 30

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/nix-verify.yml

@@ -28,7 +28,7 @@ jobs:
           name: ".+[Ss]urveyor-\\d.+"
           name_is_regexp: true
           path: gha-artifact
-      - uses: cachix/install-nix-action@v29
+      - uses: cachix/install-nix-action@v30
         with:
           extra_nix_config: |
             extra-substituters = https://cache.garnix.io