clean_duplicate_history does not clean the history of deleted model instances

[dzonecat]

Describe the bug
The management command clean_duplicate_history does only clean the history of model instances that exist. The documentation gives no indication to assume deleted model instances are excluded from cleaning.

To Reproduce

1. Save a history-enabled model instance multiple times without changing values
2. Delete the instance
3. Run clean_duplicate_history
4. Inspect the models history table in the database and find history entries with type ~ and unchanged data.

Expected behavior
History of deleted model instances is cleaned.

Environment:

• Django Simple History Version: 3.7.0
• Django Version: 5.1.4
• Database Version: PostgreSQL 15.4
• Python Version: 3.12.6