Remove unused import from doctest

Signed-off-by: John Nunley <dev@notgull.net>

src/lib.rs

@@ -785,7 +785,7 @@ pub trait Listener<T = ()>: Future<Output = T> + __sealed::Sealed {
  /// # Examples
  ///
  /// ```
- /// use event_listener::{Event, IntoNotification, Listener};
+ /// use event_listener::{Event, Listener};
  ///
  /// let event = Event::new();
  /// let mut listener1 = event.listen();