Warning "Line is no longer supported..." appears when opening Prefab Mode from Cannot restructure Prefab instance" pop-up

Steps to reproduce:

1. Create a new project using Universal 3D template
2. In the Hierarchy, create a Cube GameObject
3. Drag it to the Project window to create a prefab
4. Open the prefab in context (double-click from Project window)
5. Add another GameObject as a child of Cube (e.g. Sphere)
6. Exit prefab context
7. In the Hierarchy, expand the Cube prefab GameObject
8. Drag the child of prefab (Sphere) to the Project window
9. Observe the "Cannot restructure Prefab instance" pop-up apears and click "Open Prefab"
10. Observe the Console

Alternatively

1. Open the attached project and "SampleScene"
2. In the Hierarchy, expand the "Cube" GameObject
3. Drag the child of "Cube" (Sphere) to the Project window
4. Observe the "Cannot restructure Prefab instance" pop-up apears and click "Open Prefab"
5. Observe the Console

Actual results: "Line is no longer supported as a way to enter Prefab Mode in Context. Instead use PrefabStageUtility.OpenPrefab" warning appears

Expected results: No warnings

Reproducible with versions: 6000.4.0a5, 6000.4.1f1, 6000.5.0b2, 6000.6.0a1

Not reproducible with versions: 6000.3.12f1, 6000.4.0a4

Tested on (OS): Windows 11

Notes:

• On some versions, "Internal: JobTempAlloc has allocations that are more than the maximum lifespan of 4 frames old" warning appears as well