How to close a callout for MKAnnotation in a MKMapView

In case you want to stick with the map kit documentation.

for (NSObject<MKAnnotation> *annotation in [mapView selectedAnnotations]) {
    [mapView deselectAnnotation:(id <MKAnnotation>)annotation animated:NO];
}

The objects in selectedAnnotations are instances of MKAnnotation

NSArray *selectedAnnotations = mapView.selectedAnnotations;
for(id annotation in selectedAnnotations) {
    [mapView deselectAnnotation:annotation animated:NO];
}