I wrote a sentence inside "How to sort" to described what happens if
option "output unique lines only" is set.

Signed-off-by: Conrad Zelck <git@simpel.cc>

Buttons said 'unique' too. But after making the lines unique as an
option to check it had to be removed from the button labels. Had to be
removed from the details 'How to sort' too.

Signed-off-by: Conrad Zelck <git@simpel.cc>