build(deps): bump cachix/cachix-action from 12 to 14

Bumps [cachix/cachix-action](https://github.com/cachix/cachix-action) from 12 to 14.
- [Release notes](https://github.com/cachix/cachix-action/releases)
- [Commits](https://github.com/cachix/cachix-action/compare/v12...v14)

---
updated-dependencies:
- dependency-name: cachix/cachix-action
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

.github/workflows/nix-flake-check.yml

@@ -18,7 +18,7 @@ jobs:
           experimental-features = nix-command flakes
           access-tokens = github.com=${{ secrets.GITHUB_TOKEN }}
           system-features = nixos-test benchmark big-parallel kvm
-    - uses: cachix/cachix-action@v12
+    - uses: cachix/cachix-action@v14
       with:
         name: dadada
         signingKey: '${{ secrets.CACHIX_SIGNING_KEY }}'