[3.9] Fix error in argparse documentation example (GH-17399) (GH-21992)



Automerge-Triggered-By: @rhettinger
(cherry picked from commit 8784d3300ec4ffc58bc0e9ab3cff9a24187dbe4c)


Co-authored-by: SarahPythonista <4283226+SarahPythonista@users.noreply.github.com>
1 file changed