message: docs(concatMap): fix example
  Closes
diff: @@ -41,7 +41,7 @@ export function concatMap<T, R, O extends ObservableInput<any>>(project: (value:
  *
  * const clicks = fromEvent(document, 'click');
  * const result = clicks.pipe(
  - * concatMap(ev => interval(1000).pipe(take(4)),
  + * concatMap(ev => interval(1000).pipe(take(4)))
  * );
  * result.subscribe(x => console.log(x));
  *
  