`Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll` is included in output of framework-dependent unpackaged app

### Describe the bug

`Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll` is copied to the publish output of unpackaged apps, despite not being relevant (it only applies to packaged apps).

### Steps to reproduce the bug

1. Create a new C# app using the `WinUI Blank App (Packaged)` template
2. Add `None` to the csproj
3. (optional) Enable NAOT by also adding `true` and upgrading the target framework to .NET 9 (this removes a lot of stuff from the output, making the issue more apparent)
4. Set the build configuration to `Release` in VS
5. In the solution explorer, right click on the project and hit publish. Then in the window that opens, hit publish, and once it finishes, hit navigate to open the published directory
6. Observe the presence of `Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll`

### Expected behavior

This DLL should not be present

### Screenshots


### NuGet package version

Windows App SDK 1.7.1: 1.7.250401001

### Packaging type

Unpackaged

### Windows version

Windows 11 version 24H2 (22621, October 2024 Update)

### IDE

Visual Studio 2022-preview

### Additional context

_No response_

Start with the project's .csproj and reproduce the Release publish using the six steps in the issue, then trace which publish or packaging entry point adds Microsoft.Windows.ApplicationModel.Background.UniversalBGTask.dll. Compare unpackaged and packaged outputs; done means the DLL is absent from the unpackaged publish output while the relevant packaged behavior remains unchanged.

Written by the indexing model from the issue text.