chore(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](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]>

.github/workflows/nightly.yml

@@ -55,7 +55,7 @@ jobs:
             experimental-features = nix-command flakes
 
       - name: Setup Cachix
-        uses: cachix/cachix-action@v12
+        uses: cachix/cachix-action@v14
         with:
           name: ${{ env.CACHE_NAME }}
           authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"

.github/workflows/test.yml

@@ -38,7 +38,7 @@ jobs:
             substituters = ${{ env.SUBSTITUTERS }}
             experimental-features = nix-command flakes
       - name: Setup Cachix
-        uses: cachix/cachix-action@v12
+        uses: cachix/cachix-action@v14
         with:
           name: ${{ env.CACHE_NAME }}
           authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"