Remove outdated comments in coll_basic_reduce_scatter.c.

Refs trac:1559

This commit was SVN r29566.

The following Trac tickets were found above:
  Ticket 1559 --> https://svn.open-mpi.org/trac/ompi/ticket/1559

ompi/mca/coll/basic/coll_basic_reduce_scatter.c

@@ -60,10 +60,6 @@
  * halving is used to be nice to the app memory wise.  There are much
  * better algorithms for large messages with cummutative operations,
  * so this should be investigated further.
- *
- * NOTE: We default to a simple reduce/scatterv if one of the rcounts
- * is zero.  This is because the existing algorithms do not currently
- * support a count of zero in the array.
  */
 int
 mca_coll_basic_reduce_scatter_intra(void *sbuf, void *rbuf, int *rcounts,