updated the logging logic when running retention delete with archivin…

[paullizer]

Issue Description

The retention policy deletion process was logging errors when attempting to delete conversations or documents that had already been deleted (e.g., by another process or user action between the query and delete operations).

Error Observed

DEBUG: [Log] delete_aged_conversations_deletion_error -- {'error': '(NotFound) Entity with the specified id does not exist in the system.

Root Cause

This is a race condition scenario where:

1. The retention policy queries for aged conversations/documents
2. Between the query and the delete operation, the item is deleted by another process (user action, concurrent retention execution, etc.)
3. The delete operation fails with CosmosResourceNotFoundError (404 NotFound)