[docs] argparse required arguments displayed under "optional arguments" (issue 9694)

[vadmium+py at gmail.com]

https://bugs.python.org/review/9694/diff/13424/Doc/library/argparse.rst
File Doc/library/argparse.rst (right):

https://bugs.python.org/review/9694/diff/13424/Doc/library/argparse.rst#newcode1711
Doc/library/argparse.rst:1711: "positional arguments" and "options" when
displaying help
Maybe I should also add a “Changed in version 3.5” notice for this

https://bugs.python.org/review/9694/