build(deps): bump cachix/cachix-action from 15 to 16 (#13074)

Bumps [cachix/cachix-action](https://github.com/cachix/cachix-action) from 15 to 16.
- [Release notes](https://github.com/cachix/cachix-action/releases)
- [Commits](https://github.com/cachix/cachix-action/compare/v15...v16)

---
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>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

.github/workflows/cachix.yml

@@ -17,7 +17,7 @@ jobs:
       uses: cachix/install-nix-action@v30
 
     - name: Authenticate with Cachix
-      uses: cachix/cachix-action@v15
+      uses: cachix/cachix-action@v16
       with:
         name: helix
         authToken: ${{ secrets.CACHIX_AUTH_TOKEN }}