scheduled_task : Remove flags code

The scheduled task code is still internally implementing the concept of flags, which is entirely a V1 concept.

Flags are irrelevant to V2, and the only feature that the module currently cares about is the enabled / disabled status for a task. Remove the current flags functionality, replacing it with manipulating the enabled / disabled setting instead.

Some of this work was done already in https://github.com/puppetlabs/puppetlabs-scheduled_task/commit/1cd59136e50524e3b2ac2aa5fe63b5b9d189d453

This ticket will remove that constant completely as its only used internally and not in the scheduled_task type OR the actual V2 APIs.