Add Behaviour dropdown has a part in which the dropdown outline is cut out when the Add Behaviour dropdown is opened

Steps to reproduce:

1. Create a new Unity project using the Universal 3D template
2. Create a new Cube GameObject (GameObject > 3D Object > Cube)
3. Open the Animation window (Window > Animation > Animation)
4. Create a new Animation
5. Open the Animator window (Window > Animation > Animator)
6. Select any State
7. Click the "Add Behaviour" button in the Inspector window
8. Observe the Add Behaviour dropdown's outline

Actual results: There is a part in the dropdown in which the outline is cut off

Expected results: The outline is consistent around all of the dropdown

Reproducible with versions: 6000.0.60f1, 6000.2.8f1, 6000.3.0b6, 6000.4.0a2

Tested on (OS): MacOS Silicon Sequoia 15.6.1