Remove old `ControlPlane` managed objects deletion logic

[pmalek]

Problem statement

#2227 added the deletion of old ControlPlane managed objects to make the migration between KGO and KO smoother (less manual steps).

This issue tracks the removal of that logic (as most of the users would be migrated by the time we want to solve this

Acceptance criteria

• Old ControlPlane managed objects deletion logic is removed.