Add conditional to test for the end of the fade-out animation

Closes #3166

- Checks the name of the animation that just ended, so the notification is only removed when the `fade-out` is removed

Related styles (but not needed for this to work) are https://github.com/TryGhost/Ghost-UI/commit/220414b1b2c9f3711737dab9e38496ef9483c07a