fix: help command spacing when scriptName is empty

[CupOfTea696]

When settings the scriptName to an empty string, the help command will add an unnecessary whitespace before commands, and wrap the command usage string 1 character too early. This PR fixes this.

[CupOfTea696]

Example:

When using

yargs()
  .scriptName('')
  .command('group', 'Rule groups')
  .command('rule', 'Rule management')
  .command('help [command] [subcommand]', 'Show help')

Output:

Commands:
   group                       Rule groups
   rule                        Rule management
   help [command] [subcommand  Show help
  ]

With fix:

Commands:
  group                        Rule groups
  rule                         Rule management
  help [command] [subcommand]  Show help

[bcoe]

@CupOfTea696 thank you for the contribution 👏 right now this looks to be breaking a couple tests, mind taking a look?

[CupOfTea696]

@bcoe That should fix it.