message: docs(client): fix missing feature attrs in another doctest
  when testing my fix for I noticed that this doctest has the same issue,
  so here's another fix.
diff: //! [full client example](https://github.com/hyperium/hyper/blob/master/examples/client.rs).
  //!
  //! ```
  +//! # #[cfg(all(feature = "tcp", feature = "client", any(feature = "http1", feature = "http2")))]
  +//! # async fn fetch_httpbin() -> hyper::Result<()> {
  //! use hyper::{body::HttpBody as _, Client, Uri};
  //!
  -//! # #[cfg(feature = "tcp")]
  -//! # async fn fetch_httpbin() -> hyper::Result<()> {
  //! let client = Client::new();
  //!
  //! // Make a GET /ip to 'http://httpbin.org'
  