Nested ORM-mode models can no longer be initialized from nested dictionaries

Nested ORM-mode models can no longer be initialized from nested dictionaries: a task in MiMo-V2.6-RL-harbor-code: MiMo-V2.6-RL Code (Harbor) (Harbor dataset). I mentioned this as a comment on https://github.com/samuelcolvin/pydantic/pull/2718 but since it's already merged I figured I should open…