Fix 'j' and 'k' not working in the bionics menu.

Bionics assigned to the letters 'j' and 'k' were unable to be activated
or examined. Reassigning them to another letter worked. This seems to be
because the code tries to get UP and DOWN actions, and 'j' and 'k' are
mapped to those. The UP and DOWN actions should move the list or
selection up and down, but using the up and down key has absolutely no
effect in the bionics menu, even though in the code it looks like it should.
So I just removed the code checking for UP and DOWN actions, and now
bionics assigned to 'j' and 'k' are working as they should.

Or is it possible to get the input system to recognize 'j'/'k' and down/up arrow as different inputs? It should be possible, but I haven't been able to figure out how.