Fix cleanup docs

[alenkacz]

No description provided.

[nfnt]

Hmm, IMO finalizers are an implementation detail to ensure that a cleanup plan is run during deletion. So the goal is to run a cleanup plan and the existing documentation covers that. WDYT?

[alenkacz]

@nfnt the fact that a cleanup plan is executed is not a concern of controller anymore, that is an implementation detail of startExecutionPlan so I would say we either drop that bubble altogether or leave the finalizers there as that's the only code concerning controller right now

Actually this is obsolete as well, as that part does not start any plan anymore
2. Check if the object is being deleted, start cleanup plan

[nfnt]

You're right, these decisions are done by the Instance, ahem, instance, not the controller. 👍