Reproduction steps:
1. Open the attached “LayoutGroupBugReplication.zip” project
2. Make sure “Auto Save” option is unchecked in the Project Settings
3. Double click on the “Test_Layout.prefab” from the Project Window (Assets > Prefabs)
4. Observe the opened Prefab Mode Scene

Expected result: The Scene is not marked as dirty
Actual result: The Scene is marked as dirty

Reproducible with: 6000.0.2f1, 6000.0.12f1
Not reproducible with: 2021.3.41f1, 2022.3.39f1, 6000.0.1f1

Reproducible on: Windows 11
Not reproducible on: no other environment tested

Notes:
- Does not reproduce if the Horizontal Layout Group Component is disabled
- What seems to be the dirtying change is recorded in Edit -> Undo as "Driving RectTransform”