Global help option type is wrong

[jvalkeal]

Feature added in #582 prints:

$ java -jar spring-shell-samples/build/libs/spring-shell-samples-3.0.0-SNAPSHOT.jar help -h
NAME
       help - Display help about available commands

SYNOPSIS
       help --command String --help String

OPTIONS
       --command or -C String
       The command to obtain help for.
       [Optional]

       --help or -h String
       help for help
       [Optional]

where --help and -h is just a flag, it doesn't have a type String.