Describe the bug
A minor issue where the top margin of the icon is slightly too large, causing the icon to appear off-center when the CommandBar is collapsed
Screenshots

The icon on the left is centered (fixed)
The icon on the right is the one without any changes
Desktop/Platform
- OS: Windows 11
- FluentAvalonia Version: 2.3.0
- Avalonia Version: 11.2.6
Additional context

The margin on the ContentViewbox is too large on the top. We need to shave off 2px from the top in order to center the button changing margin from 16px to 14px