How to reproduce:
1. Create a new Unity project and install the Visual Effect Graph package
2. In the Project window, right-click -> Create -> Visual Effects -> Visual Effect Graph -> Any graph -> Create
3. Navigate to the "Update Particles" block
4. Hover on any field
5. Observe the tooltip

Expected results: The tooltip is consistent with the rest of the Editor and has the same borders from all sides
Actual results: The bottom side border has two lines

Reproducible with: 6000.0.39f1, 6000.1.0b7, 6000.2.0a4

Reproducible on: macOS Sequoia 15.3 (M1), Windows 11
Not reproducible on: No other environment tested