Removing the thin lines around each feature in widget

Hi I have used the widget with the twenty seventeen theme and have a set of lines at the top and bottom of each feature

I would like to remove them.

I have set the border colour to white and set the border size to 0 in the Design tab and it does not seem to turn it off.

I am guessing there is a css method I’m missing

Friends of Atlantis

All help greatly appreciated