Change bone vert shader to avoid code causing compiling errors on same ATI cards

My ati card, and possibly others, have a problem with the following
syntax: array1[function(array2[variable])] Replaceing the variable with a
constant will not cause the issue, but that specific syntax seems to cause
errors with some of the old ATI stuff. It may also be a problem with some
newer AMD cards, but that has zero evidence to back it up.
Signed-off-by: Unknownloner <Unknownloner.Online@gmail.com>