refactor: Remove DeregisterOperatorOperatorSets function

[maximopalopoli]

What Changed?

This PR removes DeregisterOperatorOperatorSets from avsRegistry's chainWriter. The reason of this is that should not be part of SDK, since new flow's deregisterOperator should not be accessed from any other location than the AllocationManager. This is because the register operator method of the new flow can only be called from there (otherwise there will be raised an OnlyAllocationManager() error). Thus, in the new flow the entry points to the operators registration or deregistration to AVSs should be RegisterForOperatorSets to register and DeregisterFromOperatorSets to deregister.

Reviewer Checklist

• Code is well-documented
• Code adheres to Go naming conventions
• Code deprecates any old functionality before removing it