In this patch I added the '_()' localization to the '_VersionAction' default 'help'.

While this is a straight forward change, I haven't tested it.  It does run test_argparse.py, but that doesn't have any tests for localization.

According to the discussion here:
https://mail.python.org/pipermail/python-dev/2010-May/100215.html
this default help was originally None, and adding this string was seen
as a worthwhile convenience.  Localization was not considered.

Does this use of _() really save the user effort?  May be it would if they are already using the depricated version.  Otherwise they could just give the version argument their own non default help line.  I haven't used localization enough to know.