Prefab override bold lines appear on unchanged Serialized Dictionary elements when an entry is removed or added in a prefab instance

Steps to reproduce:
1. Open the attached “IN-149494” project
2. Open the “Mission” scene
3. In the Hierarchy, select the “GameObject” GameObject
4. In the Inspector, expand the "List value Dict" dropdown
5. Select the "Water" key element, then click the lower minus (–) button to delete it
6. Observe that the bold override line stays on the element before the one that was deleted

Actual result: Bold override lines incorrectly appear on unchanged Serialized Dictionary elements when an entry is removed or added in a prefab instance
Expected result: Bold override lines should only appear on elements that have actually been modified in the prefab instance, not on elements that already exist in the Prefab

Reproducible with: 6000.6.0a6, 6000.6.0b5, 6000.7.0a3
Could not test with: 6000.0.1f1, 6000.0.80f1, 6000.3.20f1, 6000.5.5f1, 6000.6.0a5 (serialized Dictionary field doesn't exist)

Reproducible on: MacOS 26.5 (M1) , Windows 11 (By Reporter)
Not reproducible on: No other environments tested

Note: If Prefab asset gets modified to be identical to the prefab instance in the scene, the bold line still persists