Fix: Remove function prop from client component

Remove onSuccess callback from SyncRoyalMailButton since event handlers
cannot be passed to client components from server components. The button
already shows success/error messages, so the callback wasn't necessary.

src/app/admin/orders/[id]/page.tsx

@@ -150,10 +150,6 @@ export default async function OrderDetailPage({ params }: { params: { id: string
             <SyncRoyalMailButton
               orderId={order.id}
               trackingNumber={order.trackingNumber}
-              onSuccess={() => {
-                // In a real app, we'd refresh the page or update state
-                console.log('Tracking synced successfully');
-              }}
             />
           </div>
         )}