ThIt is considered to be a help for people, because when they scroll down, they loose the header of the table with the labels. So I seriously would recommend to leave it there. Usually it is less of a problem if you have a simple scale from 1-5 or something. But when the wording of the labels is important, I would think about leaving it.
Enough "advice"!
If you want to get rid of it, this is simple. Go to "global settings" -> "Miscellaneous" and change the figure at "Number of answers to show before repeating the headings in array question" from 25 to whatever value you consider best. I am not sure what will happen if you leave it empty...