remove `significance` column from output

[Indrajeet Patil]

First need to think about how to handle this context and then this can be easily done:
https://github.com/IndrajeetPatil/ggstatsplot/blob/e4a435dd421f56a6419efc3dd7b11f8f01196fbf/R/helpers_ggbetweenstats_graphics.R#L206-L222