gh-101472: Add nargs='...' to the reference of add_argument in argparse

[ppaez]

This provides a fix to improve the documentation.

• Issue: Add nargs='...' to the reference of add_argument in argparse #101472

[hpaulj]

This patch conflicts with a more recent one, #103582

argparse.REMAINDER is ...

We can't both remove all references to REMAINDER and add it's literal value back in.

Subparsers use 'argparse.PARSERwhich is 'A...'. It's a validnargsvalue, but only used by the_SubParsersActionclass. Not all possiblenargs` values have to be documented.

[hauntsaninja]

Thanks for the PR, and thanks hpaulj for linking to the other PR.

However, I left a comment on #101472 (comment) mentioning what I think the ways forward for this are.