message: docs(client): fix typo in httpbin.org domain
diff: @@ -147,7 +147,7 @@ where
  ///
  /// let req = Request::builder()
  /// .method("POST")
  - /// .uri("http://httpin.org/post")
  + /// .uri("http://httpbin.org/post")
  /// .body(Body::from("Hallo!"))
  /// .expect("request builder");
  ///
  