scheduled_task : Remove spec folder from shipped module

The module contains extraneous code that is not necessary in the spec folder.

In particular, some legacy code that has been removed from Puppet 6 was restored to the module, solely to confirm compatibility between the old provider on the v1 COM APIs and the new providers which use v2 APIs.  That code was migrated in as part of https://github.com/puppetlabs/puppetlabs-scheduled_task/pull/55

I'm not sure if the Puppet loader searches the spec directory when loading code (when module is installed via PMT or pluginsync methods), but we probably don't want the legacy code to still be available in Puppet 6. There shouldn't be any complications to having this code available, but it would be better to have it fully removed.

An easy solution here should be to remove the spec directory from the shipped module tarball as part of the packaging step.