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](cachix/cachix-action@v12...v14)

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

.github/workflows/build_nix.yml

@@ -24,7 +24,7 @@ jobs:
       - name: Install Nix
         uses: cachix/install-nix-action@v25
 
-      - uses: cachix/cachix-action@v12
+      - uses: cachix/cachix-action@v14
         with:
           name: espresso-systems-private
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'