textproc/rubygem-puppet-strings: Update to 4.1.0

While here, default to sysutils/puppet8 to provide Puppet and drop
broken option to use sysutils/puppet6 which does not exist anymore.

ChangeLog:
https://github.com/puppetlabs/puppet-strings/blob/main/CHANGELOG.md#v410---2023-07-04

With hat: puppet