Fix warp fullstack adapter

packages/fullstack/examples/warp-hello-world/src/main.rs

@@ -50,8 +50,6 @@ fn app(cx: Scope<AppProps>) -> Element {
 async fn post_server_data(data: String) -> Result<(), ServerFnError> {
     // The server context contains information about the current request and allows you to modify the response.
     let cx = server_context();
-    cx.response_headers_mut()
-        .insert("Set-Cookie", "foo=bar".parse().unwrap());
     println!("Server received: {}", data);
     println!("Request parts are {:?}", cx.request_parts());