[docs] [issue27992] Clarify %(prog)s in argparse help formatter returns basename of sys.argv[0] by default

Change by py.user <bugzilla-mail-box@yandex.ru>: ---------- pull_requests: +12642 stage: -> patch review _______________________________________ Python tracker <report@bugs.python.org> <https://bugs.python.org/issue27992> _______________________________________