[MU4 Issue] Z-fighting can occur when expanded palette just barely cuts off

[KokonoeTooru]

When expanded palette just barely cuts off, z-fighting (flashing) can occur

Steps to reproduce the behavior:

1. Expand all palette
2. Scroll down until a palette barely cuts off
3. Z-fighting happened

Expected behavior: No flashing

Example:

https://user-images.githubusercontent.com/52397082/209438016-6a25b630-0f81-4685-a53f-1a83dc2b50b5.mp4

Platform information:

• OS: Windows 10 21H2
• MuseScore 4.0.0.223472200

[cbjeukendrup]

Looks like a problem similar to #11333