XAML content hosted by DesktopWindowXamlSource has a diagonal white line when resizing it

### Describe the bug

While resizing XAML content hosted by DesktopWindowXamlSource a white diagonal line is displayed

### Steps to reproduce the bug

1. Resize a XAML windows
2. Observe a white line

### Expected behavior

No white line appears

### Screenshots

https://github.com/user-attachments/assets/63c91e3d-bc0f-4693-9bf8-97d3552b3d98
https://github.com/user-attachments/assets/7b51087c-2005-4c92-985e-2b08194f86c7

### NuGet package version

WinUI 3 - Windows App SDK 1.7.3: 1.7.250606001

### Windows version

Windows Insider Build (xxxxx), Windows 11 (24H2): Build 26100

### Additional context

Note: It does not display on CoreWindow

Start by reproducing the diagonal white line while resizing XAML content hosted by DesktopWindowXamlSource on Windows App SDK 1.7.3, then compare the behavior with CoreWindow, where the issue reports no line. Done means the line no longer appears during resizing; no source file or test is identified in the issue.

Written by the indexing model from the issue text.