Look up the API documentation of class JacksonFactory.
It tells you what to do:
Deprecated.
use com.google.api.client.json.GsonFactory instead
Looking into the API documentation of class GsonFactory
you see, its API methods are compatible to those of JacksonFactory,
since both extend from the same superclass JsonFactory.
(Only their internal implementations are different, of course.)
Therefore it is simple to change your code. Just to replace the line
private static final JsonFactory JSON_FACTORY = JacksonFactory.getDefaultInstance();
by
private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();