message: make the headers test no_run until demo.nats.io uses the next release
diff: @@ -644,7 +644,7 @@ impl Connection {
  /// Publish a message which may have a reply subject or headers set.
  ///
  /// # Example
  - /// ```
  + /// ```no_run
  /// # fn main() -> std::io::Result<()> {
  /// # let nc = nats::connect("demo.nats.io")?;
  /// let sub = nc.subscribe("foo.headers")?;
  