Add missing \versionadded.
 (backport from rev. 56006)
diff --git a/Doc/api/concrete.tex b/Doc/api/concrete.tex
index 8aa9b0f..ec3d84a 100644
--- a/Doc/api/concrete.tex
+++ b/Doc/api/concrete.tex
@@ -99,6 +99,7 @@
 
 \begin{csimplemacrodesc}{Py_RETURN_NONE}
   Properly handle returning \cdata{Py_None} from within a C function.
+  \versionadded{2.4}
 \end{csimplemacrodesc}