Bump picocli version to 3.2.0 from 3.1.0

Many improvements. For Groovy users, perhaps most interesting is better support for completion candidates (both bash completion scripts and JLine interactive applications). 

The description for options and positional parameters can contain variables that expand to the default value or completion candidates.

For more details, see https://github.com/remkop/picocli/releases/tag/v3.2.0