Clarify expectedFailure in the unittest docs. (GH-10953)

(cherry picked from commit 91f259b478ae8bfb4c73e5b5a767e4bf0ee9257f)

Co-authored-by: Gregory P. Smith <greg@krypto.org>
diff --git a/Doc/library/unittest.rst b/Doc/library/unittest.rst
index fb5bd2b..774b087 100644
--- a/Doc/library/unittest.rst
+++ b/Doc/library/unittest.rst
@@ -585,8 +585,8 @@
 
 .. decorator:: expectedFailure
 
-   Mark the test as an expected failure.  If the test fails when run, the test
-   is not counted as a failure.
+   Mark the test as an expected failure.  If the test fails it will be
+   considered a success.  If the test passes, it will be considered a failure.
 
 .. exception:: SkipTest(reason)