message: docs(aio): fix path to observables guide
  PR Close
diff: @@ -439,7 +439,7 @@ Observables can deliver single or multiple values of any type to subscribers, ei
  Angular uses a third-party library called [Reactive Extensions (RxJS)](http://reactivex.io/rxjs/).
  -To learn more, see the [Observables](guide/glossary#observable) guide.
  +To learn more, see the [Observables](guide/observables) guide.
  {@a observer}
  