Update Doc/using/cmdline.rst

Co-authored-by: Victor Stinner <vstinner@python.org>

Author: pablogsal

Doc/using/cmdline.rst

@@ -1105,7 +1105,7 @@ conflict.
       and kill the process.  Only enable this in environments where the
       huge-page pool is properly sized and fork-safety is not a concern.
 
-   .. versionadded:: 3.15
+   .. versionadded:: next
 
 
 .. envvar:: PYTHONLEGACYWINDOWSFSENCODING