sysutils/rubygem-bolt: Update to 3.27.4

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/bolt/blob/main/CHANGELOG.md#bolt-3274-2023-10-05

With hat: puppet