bpo-41325: Add version note for args and kwargs property in call object (GH-21525)

diff --git a/Doc/library/unittest.mock.rst b/Doc/library/unittest.mock.rst
index 3643d1a..c5360f9 100644
--- a/Doc/library/unittest.mock.rst
+++ b/Doc/library/unittest.mock.rst
@@ -647,6 +647,9 @@
         arguments and make more complex assertions. See
         :ref:`calls as tuples <calls-as-tuples>`.
 
+        .. versionchanged:: 3.8
+           Added ``args`` and ``kwargs`` properties.
+
 
     .. attribute:: call_args_list