I'm not sure if there's a language string for the validity. There is for the ", then", but I believe it's just "%s, then %s" and you can't remove a %s without breaking the sprintf. You can hide the validity column though within CBSubs > Settings > Display > Baskets and adjusting the basket display at the bottom (recommend setting to default display). I've created a bug ticket for further investigation of the issue.
#5009