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

(cherry picked from commit 6860629d)
Co-authored-by: Andrés Delfino <adelfino@gmail.com>

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::