Recurring logic does not clean up sync plan relationship when unset
Fixes #34660: Reload old recurring logic when updating sync plan
A change in Rails 6.0.4+ results in the old recurring logic retaining
a reference to the sync plan such that when the recurring logic is
cancelled, which triggers a save, that save resets the relationship
of sync plan to recurring logic. The resulting sync plan winds up
related to the old recurring logic instead of the new.