The Blackboard window has no scrollbar when there are many objects in the Blackboard window

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Install the Behavior package (com.unity.behavior)
3. Create a new Blackboard (Assets > Create > Behavior > Blackboard)
4. Open the newly created Blackboard
5. Create a lot of elements until they don't fit in the Blackboard window
6. Observe the Blackboard window

Actual results: The Blackboard window has no scrollbar

Expected results: The Blackboard window has a scrollbar

Reproducible with versions: 1.0.13 (6000.0.61f1, 6000.2.10f1, 6000.3.0b9, 6000.4.0a4)

Tested on (OS): MacOS Silicon Sequoia 15.6.1, Windows 11