The -not option with no arguments now outputs error instead of stack trace

[apainintheneck]

Checklist

• I have read the contributing doc.
• I have included a link to the relevant issue number.
• I have checked to ensure there aren't other open pull requests
  for the same issue.
• I have written new tests for these changes, as needed.

This is related to the bug discussed in #1350. By setting nargs=1 argparse now automatically checks to see if that you've entered the right number of arguments and that prevents [None] from being passed to interior methods. As a result, the user gets an argument error when trying to pass too few arguments.

usage: jrnl [--debug] [--help] [--version] [--list] [--encrypt] [--decrypt] [--import] [-on DATE] [-today-in-history] [-month DATE] [-day DATE] [-year DATE]
            [-from DATE] [-to DATE] [-contains TEXT] [-and] [-starred] [-n [NUMBER]] [-not TAG] [--edit] [--delete] [--format TYPE] [--tags] [--short]
            [--config-override CONFIG_KV_PAIR CONFIG_KV_PAIR] [--config-file CONFIG_FILE_PATH]
            [...]
jrnl: error: argument -not: expected 1 argument

Fixes #1350.

[wren]

Looks great. Thank you!