Update an obsolete comment about trx commit: we can no longer call trx_undo_update_cleanup_by_discard(), and actually, the idea to call it was erroneous, it cannot work


innobase/trx/trx0trx.c:
  Update an obsolete comment about trx commit: we can no longer call trx_undo_update_cleanup_by_discard(), and actually, the idea to call it was erroneous, it cannot work
innobase/trx/trx0undo.c:
  Update an obsolete comment about trx commit: we can no longer call trx_undo_update_cleanup_by_discard(), and actually, the idea to call it was erroneous, it cannot work
innobase/include/trx0undo.h:
  Update an obsolete comment about trx commit: we can no longer call trx_undo_update_cleanup_by_discard(), and actually, the idea to call it was erroneous, it cannot work