[BUG] `state:modified` false positive for unchanged Python models

[dataders]

Description

When running dbt build --select state:modified with deferral, Python models that have not changed are incorrectly selected and run.

Steps to Reproduce

1. Do a full build and save the manifest as the deferred state
2. Change nothing
3. Run dbt build --select state:modified with deferral to the saved manifest
4. Observe: unchanged Python models are selected and run

Expected Behavior

Unchanged Python models should not be selected by state:modified.

Actual Behavior

Python models are always treated as modified regardless of whether their definition has changed.

[mikaylacrawford]

Thanks for filing Anders! Here's the specific commit on my test project for reproducing: https://github.com/dbt-labs/orc-jaffle-shop/pull/15/changes/627c695bbf070cc0db34e361702192785383a497