Merge #20145 backport: delete whatsnew entry.

Doc/whatsnew/3.5.rst

@@ -192,9 +192,3 @@ that may require changes to your code.
   if it represented midnight in UTC.  This behavior was considered obscure and
   error-prone and has been removed in Python 3.5.  See :issue:`13936` for full
   details.
-
-* :meth:`unittest.TestCase.assertRaisesRegex` and
-  :meth:`~unittest.TestCase.assertWarnsRegex` now raise a :exc:`TypeError` if
-  the second argument is not a string or a compiled :mod:`regex`.  You may have
-  tests with an invalid second argument that have until 3.5 been falsely
-  passing which will now raise TypeErrors (:issue:`20145`).