Fix whitespace.

Doc/lib/libitertools.tex

@@ -250,7 +250,7 @@ by functions or loops that truncate the stream.
   third line).  Equivalent to:
 
   \begin{verbatim}
-     def islice(iterable, *args):    
+     def islice(iterable, *args):
          s = slice(*args)
          it = iter(xrange(s.start or 0, s.stop or sys.maxint, s.step or 1))
          nexti = it.next()