Fix incorrect comment in proxy-simple example (#1066)

examples/proxy-simple/src/main.rs

@@ -6,7 +6,7 @@ async fn main() {
 
     // In this example, if the requested URL begins with <http://127.0.0.1:5800/>, the proxy goes to
     // <https://www.rust-lang.org>; if the requested URL begins with <http://localhost:5800/>, the proxy
-    // goes to <https://www.rust-lang.org>.
+    // goes to <https://crates.io>.
     let router = Router::new()
         .push(
             Router::new()