As per documentation and examples, the new way is:
import mbxClient from '@mapbox/mapbox-sdk';
import mbxGeocoding from '@mapbox/mapbox-sdk/services/geocoding';
const mapboxClient = mbxClient({ accessToken: MAPBOX_API });
const geocodingClient = mbxGeocoding(mapboxClient);
geocodingClient.reverseGeocode({
query: [-95.4431142, 33.6875431]
})
.send()
.then(response => {
// GeoJSON document with geocoding matches
const match = response.body;
});