Remove argument from use_hook closure (#496)

Also; update docs for said function

packages/hooks/src/usefuture.rs

@@ -25,7 +25,7 @@ where
     F: Future<Output = T> + 'static,
     D: UseFutureDep,
 {
-    let state = cx.use_hook(move |_| UseFuture {
+    let state = cx.use_hook(move || UseFuture {
         update: cx.schedule_update(),
         needs_regen: Cell::new(true),
         slot: Rc::new(Cell::new(None)),