bpo-35027, distutils doc: Correct note on setup.py change in Python 3.7 (GH-10032)

diff --git a/Doc/distutils/setupscript.rst b/Doc/distutils/setupscript.rst
index 1d96acb..c1051d2 100644
--- a/Doc/distutils/setupscript.rst
+++ b/Doc/distutils/setupscript.rst
@@ -682,9 +682,8 @@
           )
 
 .. versionchanged:: 3.7
-   :class:`~distutils.core.setup` now raises a :exc:`TypeError` if
-   ``classifiers``, ``keywords`` and ``platforms`` fields are not specified
-   as a list.
+   :class:`~distutils.core.setup` now warns when ``classifiers``, ``keywords``
+   or ``platforms`` fields are not specified as a list or a string.
 
 .. _debug-setup-script: