Non resizable window withouth title bar has border when updating to 1.6

### Describe the bug

With the 1.6 version i get a white border around a window that's not resizable.

### Steps to reproduce the bug

Create a window with the following code:
``` csharp
Window window = new();
OverlappedPresenter presenter = OverlappedPresenter.Create();
presenter.IsResizable = false;
presenter.SetBorderAndTitleBar(false, false);
window.AppWindow.SetPresenter(presenter);
window.AppWindow.Show();
```

### Expected behavior

There is no border around the window

### Screenshots


### NuGet package version

WinUI 3 - Windows App SDK 1.6.0: 1.6.240829007

### Windows version

Windows 11 (22H2): Build 22621

### Additional context

Works fine with WindowsAppSDK 1.5.240802000

Start by running the provided C# reproduction on Windows 11 with Windows App SDK 1.6, then compare it with 1.5. Investigate the window presenter behavior for a non-resizable window with both the border and title bar disabled; done means the 1.6 window has no white border, matching the expected behavior and the 1.5 result.

Written by the indexing model from the issue text.