Update docs/core/knowledge-bases.rst
Update docs/core/knowledge-bases.rst

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