fix: show options when required flag or arg is not given a value

[mdonnalley]

Fixes #1014
@W-15263147@

[cristiand391]

QA:

flags:

➜  sf-plugin-api git:(main) ./bin/dev.js org api asdf -o gs0 --method
Error (2): Flag --method expects one of these values: GET, POST, PUT, PATCH, HEAD, DELETE, OPTIONS, TRACE

➜  sf-plugin-api git:(main) sf org api asdf -o gs0 --method
Error (1): Flag --method expects a value

args:

➜  plugin-autocomplete git:(main) ✗ ./bin/dev.js autocomplete
Error: Missing 1 required arg:
shell  Shell type
See more help with --help

➜  plugin-autocomplete git:(main) ✗ ./bin/dev.js autocomplete
Error: Missing 1 required arg:
shell  (zsh|bash|powershell) Shell type
See more help with --help