Fix one versionchanged

Author: merwok

Doc/library/unittest.rst

@@ -1936,8 +1936,11 @@ Loading and running tests
    Calling ``main`` actually returns an instance of the ``TestProgram`` class.
    This stores the result of the tests run as the ``result`` attribute.
 
+   .. versionchanged:: 3.1
+      The ``exit`` parameter was added.
+
    .. versionchanged:: 3.2
-      The ``exit``, ``verbosity``, ``failfast``, ``catchbreak``, ``buffer``,
+      The ``verbosity``, ``failfast``, ``catchbreak``, ``buffer``
       and ``warnings`` parameters were added.