nix ci: cachix only on HPP org

Author: nim65s

.github/workflows/nix.yml

@@ -15,5 +15,6 @@ jobs:
       - uses: DeterminateSystems/magic-nix-cache-action@main
       - run: nix --accept-flake-config build -L
       - run: nix --accept-flake-config run .#cachix push gepetto $(readlink result)
+        if: github.repository_owner == 'humanoid-path-planner'
         env:
           CACHIX_AUTH_TOKEN: ${{ secrets.CACHIX_AUTH_TOKEN }}