restore lifetime checking for signals

examples/dog_app.rs

@@ -80,7 +80,7 @@ fn BreedPic(breed: Signal<String>) -> Element {
             .await
     });
 
-    match fut.read().as_ref() {
+    match fut.read_unchecked().as_ref() {
         Some(Ok(resp)) => rsx! {
             button { onclick: move |_| fut.restart(), "Click to fetch another doggo" }
             img { max_width: "500px", max_height: "500px", src: "{resp.message}" }