Remove duplicate words in docs. (GH-26167) (GH-26296)

(cherry picked from commit b06ed1d883cd79c920c514d8a1f4643cf93dc5e0)

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
diff --git a/Doc/library/unittest.mock.rst b/Doc/library/unittest.mock.rst
index 1604731..f1c0757 100644
--- a/Doc/library/unittest.mock.rst
+++ b/Doc/library/unittest.mock.rst
@@ -328,8 +328,8 @@
 
     .. method:: assert_called_once_with(*args, **kwargs)
 
-       Assert that the mock was called exactly once and that that call was
-       with the specified arguments.
+       Assert that the mock was called exactly once and that call was with the
+       specified arguments.
 
             >>> mock = Mock(return_value=None)
             >>> mock('foo', bar='baz')