Building with SDK 8.0.403 unexpectedly generates WinRT-related code

### Describe the bug

After updating the .NET SDK from 8.0.402 to 8.0.403, some projects that target net8.0-windows10.0.19041.0 have started generating unexpected WinRT-related code via source generator WinRT.SourceGenerator.

The generated code uses language features only available in C# 9+, which in this case causes compilation to fail, but the main issue is that this source generator generates anything at all: this is not a project that uses WinRT, and with SDK 8.0.402 this doesn't happen.

Additionally, we are seeing diagnostics `CsWinRT1028` and `CsWinRT1030`, which we do not see with 8.0.402.

### To Reproduce

See https://github.com/chris-white-wtw/dotnet-sdk-winrt-issue.

Using SDK 8.0.403, build test.csproj.

### Exceptions (if any)

No exceptions, just a compilation error:
```
C:\git\dotnet-sdk-winrt-issue\test\obj\Debug\net8.0-windows10.0.19041.0\generated\WinRT.SourceGenerator\Generator.WinRT
AotSourceGenerator\WinRTGlobalVtableLookup.g.cs(11,10): error CS8370: Feature 'module initializers' is not available in
C# 7.3. Please use language version 9.0 or greater. [C:\git\dotnet-sdk-winrt-issue\test\test.csproj]
```

### Further technical details

`dotnet --info`:

```
.NET SDK:
Version: 8.0.403
Commit: c64aa40a71
Workload version: 8.0.400-manifests.18f19b92
MSBuild version: 17.11.9+a69bbaaf5

Runtime Environment:
OS Name: Windows
OS Version: 10.0.19045
OS Platform: Windows
RID: win-x64
Base Path: c:\work\dotnet\dotnet\sdk\8.0.403\

.NET workloads installed:
Configured to use loose manifests when installing new manifests.
[aspire]
Installation Source: VS 17.10.35013.160
Manifest Version: 8.0.0-preview.1.23557.2/8.0.100
Manifest Path: c:\work\dotnet\dotnet\sdk-manifests\8.0.100\microsoft.net.sdk.aspire\8.0.0-preview.1.23557.2\WorkloadManifest.json
Install Type: FileBased

Host:
Version: 8.0.10
Architecture: x64
Commit: 81cabf2857

.NET SDKs installed:
8.0.403 [c:\work\dotnet\dotnet\sdk]

.NET runtimes installed:
Microsoft.AspNetCore.App 8.0.10 [c:\work\dotnet\dotnet\shared\Microsoft.AspNetCore.App]
Microsoft.NETCore.App 8.0.10 [c:\work\dotnet\dotnet\shared\Microsoft.NETCore.App]
Microsoft.WindowsDesktop.App 8.0.10 [c:\work\dotnet\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:
C:\git\dotnet-sdk-winrt-issue\global.json

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

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

No particular IDE - running from command line.