message: docs(client): Add tcp feature for Client::new docs
  added cfg attr to denote required tcp feature in docs for Client::new method
  Closes:
diff: @@ -59,6 +59,7 @@ impl Client<HttpConnector, Body> {
  /// The default connector does **not** handle TLS. Speaking to `https`
  /// destinations will require [configuring a connector that implements
  /// TLS](https://hyper.rs/guides/client/configuration).
  + #[cfg_attr(docsrs, doc(cfg(feature = "tcp")))]
  #[inline]
  pub fn new() -> Client<HttpConnector, Body> {
  Builder::default().build_http()
  