Well "in" is there to show the category instead of "in category:" Landscapes.
Because if you do not display title, a visitor could think it is the image's title.
That's the way also big galleries like
http://deviantart.com do it.
But if you want to remove it, you can edit the phrase.
its either phrase
in_x or simply
in (dependig where it is used)
or you could edit template adv_gallery_imgbit_lite and remove {
vb:rawphrase in} there.