Delete expired CampaignSpecs and ChangesetSpecs
Created by: mrnugget
This is the next item in the task list in https://github.com/sourcegraph/sourcegraph/pull/11675 and just simple housekeeping:
- delete
ChangesetSpecs
if they haven't been attached to aCampaignSpec
- delete
CampaignSpecs
if there is noCampaign
with a reference to them (meaning that they haven't been applied yet)