bpo-35047: Update whatsnew/3.8 for better mock error message (GH-13746)

diff --git a/Doc/whatsnew/3.8.rst b/Doc/whatsnew/3.8.rst
index f060f4b..8456a17 100644
--- a/Doc/whatsnew/3.8.rst
+++ b/Doc/whatsnew/3.8.rst
@@ -760,6 +760,9 @@
   :meth:`~unittest.TestCase.setUpClass()`.
   (Contributed by Lisa Roach in :issue:`24412`.)
 
+* Several mock assert functions now also print a list of actual calls upon
+  failure. (Contributed by Petter Strandmark in :issue:`35047`.)
+
 venv
 ----