build(deps): 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] <[email protected]>

Author: dependabot[bot]

.github/workflows/integrationtest.yml

@@ -26,7 +26,7 @@ jobs:
     steps:
       - name: Check out
         uses: actions/checkout@v4
-      - uses: cachix/install-nix-action@v29
+      - uses: cachix/install-nix-action@v30
         with:
           # This channel is only required to invoke "nix-shell".
           # Everything inside that nix-shell will use a pinned version of