Update whatsnew based on doc search.
diff --git a/Doc/library/threading.rst b/Doc/library/threading.rst
index 12cf2e8..2b66461 100644
--- a/Doc/library/threading.rst
+++ b/Doc/library/threading.rst
@@ -687,7 +687,7 @@
    This method returns the internal flag on exit, so it will always return
    ``True`` except if a timeout is given and the operation times out.
 
-   .. versionchanged:: 2.7
+   .. versionchanged:: 3.1
       Previously, the method always returned ``None``.