scheduled_task : remove random_minutes_interval

random_minutes_interval is not a real concept from the V1 task scheduler COM API because the wRandomMinutesInterval returned is always 0.

However, it has been partially implemented, and the implementation is incorrect. There is no way to translate the RandomDelay value from the V2 API to an equivalent, either in the V1 struct / API or in the intermediate representation.

Therefore, all usages of random_minutes_interval should be removed. In the V2 implementation, RandomDelay will be readable / writable via the trigger hash, but it will be exposed as the native ISO8601 duration string to end users to allow for a full fidelity representation in a future effort.

NOTE: the COM integration for the original provider lives in https://github.com/puppetlabs/puppet/blob/master/lib/puppet/util/windows/taskscheduler.rb in the Puppet repo, so the FFI struct definition cannot be modified at this point in time. That will impact how some tests are modified.