public function delete($product_id)
{
    $product = Product::findOrFail($product_id);
    if ($product->delete()) {
        $this->deleteDirectories($product_id);
        return back()->with('success', 'محصول با موفقیت حذف شد');
    }
    return back()->with('failed', 'خطا محصول حذف نشد');
}
private function deleteDirectories($product_id)
{
    $productPath = public_path('products/' . $product_id);
    $storagePath = storage_path('app/local_storage/products/' . $product_id);
    File::deleteDirectory($productPath);
    File::deleteDirectory($storagePath);
}

قبلشم این namespace رو use کنید ❗

use Illuminate\\Support\\Facades\\File;