updated help text for data export button (#3589)
updated help text for data export button (#3589)

Fixes #963
amyrebecca/Panoptes-Front-End,jelliotartz/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,jelliotartz/Panoptes-Front-End,zooniverse/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,jelliotartz/Panoptes-Front-End