bpo-36739: Update controlflow.rst (GH-12983)


in addition to global-statement also mention nonlocal-statement
(in the paragraph describing access to variables which are non local to a function
(cherry picked from commit e1f95e77e0647aff602e0660ba3c282b71045875)

Co-authored-by: pbhd <p-bauer-schriesheim@t-online.de>
1 file changed