NET 9-windows project can't project-reference a net8-windows project

### Describe the bug
If I create a .NET 8 WinUI Class library, and then reference that in a .NET 9 MAUI project, I get the following build error:

> >C:\Program Files\dotnet\sdk\9.0.101\Sdks\Microsoft.NET.Sdk\targets\Microsoft.PackageDependencyResolution.targets(266,5): error NETSDK1005: Assets file 'E:\source\WinUIClassLibraryNet8\WinUIClassLibraryNet8\obj\project.assets.json' doesn't have a target for 'net9.0-windows10.0.19041.0'. Ensure that restore has run and that you have included 'net9.0-windows10.0.19041.0' in the TargetFrameworks for your project.

### To Reproduce
- Create a WinUI .NET 8 Class Library
- Create a .NET MAUI .NET 9 Class Library
- Add a project reference to the NET8 WinUI project from the NET9 MAUI project
``
- Build the project and observe the build error mentioned above.

Repro project: [WinUIClassLibraryNet8.zip](https://github.com/user-attachments/files/18337904/WinUIClassLibraryNet8.zip)

### Exceptions (if any)

project.assets.json' doesn't have a target for 'net9.0-windows10.0.19041.0'. Ensure that restore has run and that you have included 'net9.0-windows10.0.19041.0' in the TargetFrameworks for your project.

### Further technical details
dotnet --info

.NET SDK:
Version: 9.0.101
Commit: eedb237549
Workload version: 9.0.100-manifests.4a280210
MSBuild version: 17.12.12+1cce77968

Runtime Environment:
OS Name: Windows
OS Version: 10.0.22631
OS Platform: Windows
RID: win-x64
Base Path: C:\Program Files\dotnet\sdk\9.0.101\

.NET workloads installed:
[ios]
Installation Source: VS 17.12.35527.113
Manifest Version: 18.1.9163/9.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\9.0.100\microsoft.net.sdk.ios\18.1.9163\WorkloadManifest.json
Install Type: Msi

[maui-windows]
Installation Source: VS 17.12.35527.113
Manifest Version: 9.0.0/9.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\9.0.100\microsoft.net.sdk.maui\9.0.0\WorkloadManifest.json
Install Type: Msi

[android]
Installation Source: VS 17.12.35527.113
Manifest Version: 35.0.7/9.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\9.0.100\microsoft.net.sdk.android\35.0.7\WorkloadManifest.json
Install Type: Msi

[maccatalyst]
Installation Source: VS 17.12.35527.113
Manifest Version: 18.1.9163/9.0.100
Manifest Path: C:\Program Files\dotnet\sdk-manifests\9.0.100\microsoft.net.sdk.maccatalyst\18.1.9163\WorkloadManifest.json
Install Type: Msi

Configured to use loose manifests when installing new manifests.

Host:
Version: 9.0.0
Architecture: x64
Commit: 9d5a6a9aa4

.NET SDKs installed:
8.0.404 [C:\Program Files\dotnet\sdk]
9.0.101 [C:\Program Files\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.AspNetCore.App 9.0.0 [C:\Program Files\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.NETCore.App 9.0.0 [C:\Program Files\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 6.0.36 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 7.0.20 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 8.0.11 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]
Microsoft.WindowsDesktop.App 9.0.0 [C:\Program Files\dotnet\shared\Microsoft.WindowsDesktop.App]

Other architectures found:
x86 [C:\Program Files (x86)\dotnet]
registered at [HKLM\SOFTWARE\dotnet\Setup\InstalledVersions\x86\InstallLocation]

Environment variables:
Not set

global.json file:
Not found

Learn more:
https://aka.ms/dotnet/info

Download .NET:
https://aka.ms/dotnet/download

- The IDE (VS / VS Code/ VS4Mac) you're running on, and its version: VS2022 17.12.3

### Workarounds:
Add the following to the project reference:
`TargetFramework=net8.0-windows10.0.19041.0`
or change the WinUI class library to use `TargetFrameworks` instead of `TargetFramework` which seem silly when there's just one TFM.