Update docs/api/training-data-importers.rst
Update docs/api/training-data-importers.rst

Co-Authored-By: Alan Nichol <91e38e63b890fbb214c8914809fde03c73e7f24d@rasa.com>
RasaHQ/rasa_nlu,RasaHQ/rasa_nlu,RasaHQ/rasa_nlu