github: replace deprecated nix cache action

Author: smoothprogrammer

.github/workflows/main.yaml

@@ -15,7 +15,7 @@ jobs:
       - name: Setup Nix
         uses: DeterminateSystems/nix-installer-action@main
       - name: Cache Nix
-        uses: DeterminateSystems/magic-nix-cache-action@main
+        uses: DeterminateSystems/flakehub-cache-action@main
       - name: Lint
         run: |
           nix develop ${{ env.CI_NIX_FLAKE }} --command \