Replace train file with test file

[Liranbz]

Hi, I think that this line https://github.com/Synerise/booking-challenge/blob/5929665be72eaabf2395e82e80d6b90f541eadf1/src/encoding.py#L57

should be replaced with: test = test.sort_values(['utrip_id', 'row_num'])