message: chore(CHANGELOG): remove unwanted entry
diff: * **Schedulers:** Fix issue where canceling an asap or animationFrame action early could throw ([#2638](https://github.com/ReactiveX/RxJS/issues/2638)) ([fc39043](https://github.com/ReactiveX/RxJS/commit/fc39043))
  -### BREAKING CHANGES
  -
  -* **first:** unsubscription cadence has changed for `first`, this means side-effects related to unsubscription may occur at a different time than in previous versions.
  -
  -
  <a name="5.4.0"></a>
  # [5.4.0](https://github.com/ReactiveX/RxJS/) (2017-05-09)
  