Update six to 1.14.0
Update six to 1.14.0

Update `six` package since pip v20 requires a higher version to function
learningequality/kolibri,indirectlylit/kolibri,indirectlylit/kolibri,mrpau/kolibri,learningequality/kolibri,indirectlylit/kolibri,learningequality/kolibri,learningequality/kolibri,mrpau/kolibri,mrpau/kolibri,indirectlylit/kolibri,mrpau/kolibri