Fix ratelimiting example

Geeze, that code's ancient!  How long was that broken?

examples/ratelimiting.rs

@@ -17,21 +17,18 @@ async fn main() -> Result<()> {
         .await
 }
 
-fn handle_request(request: Request) -> BoxFuture<'static, Result<Response>> {
-    async move {
-        let mut document = Document::new();
+async fn handle_request(request: Request) -> Result<Response> {
+    let mut document = Document::new();
 
-        if let Some("limit") = request.trailing_segments().get(0).map(String::as_str) {
-            document.add_text("You're on a rate limited page!")
-                    .add_text("You can only access this page twice per minute");
-        } else {
-            document.add_text("You're on a normal page!")
-                    .add_text("You can access this page as much as you like.");
-        }
-        document.add_blank_line()
-                .add_link("/limit", "Go to rate limited page")
-                .add_link("/", "Go to a page that's not rate limited");
-        Ok(Response::document(document))
+    if let Some("limit") = request.trailing_segments().get(0).map(String::as_str) {
+        document.add_text("You're on a rate limited page!")
+                .add_text("You can only access this page twice per minute");
+    } else {
+        document.add_text("You're on a normal page!")
+                .add_text("You can access this page as much as you like.");
     }
-    .boxed()
+    document.add_blank_line()
+            .add_link("/limit", "Go to rate limited page")
+            .add_link("/", "Go to a page that's not rate limited");
+    Ok(document.into())
 }