Follow-up of RHCLOUD-43571 with no specific timeline.

Acceptance criteria:

• The rhel/policies templates are removed from https://github.com/RedHatInsights/notifications-backend.
• The rhel/policies aggregation logic is removed from https://github.com/RedHatInsights/notifications-backend.
• The IQE plugin is checked and if it contains tests about Policies, they are removed.
• All traces of policies are removed as well, which will be challenging as policies is everywhere in the notifications-backend tests.