bpo-33798: Update csv document about dict order (GH-7490)

Author: andresdelfino

Doc/library/csv.rst

@@ -203,9 +203,7 @@ The :mod:`csv` module defines the following classes:
  :class:`writer` instance.
 
  Note that unlike the :class:`DictReader` class, the *fieldnames* parameter
- of the :class:`DictWriter` is not optional. Since Python's :class:`dict`
- objects are not ordered, there is not enough information available to deduce
- the order in which the row should be written to file *f*.
+ of the :class:`DictWriter` class is not optional.
 
  A short usage example::