1.13 Error timestamp

[heidygerbi]

https://github.com/angular/angularfire2/blob/master/src/firestore/firestore.ts#L21
angular/angularfire#1993

@firebase/firestore: Firestore (5.10.0): The timestampsInSnapshots setting now defaults to true and you no longer need to explicitly set it. In a future release, the setting will be removed entirely and so it is recommended that you remove it from your firestore.settings() call now.