HybridCache in .NET Framework SDK project triggers not supported warning

### Description

When building a .NET framework SDK style project this is triggered:

https://github.com/dotnet/extensions/blob/dd660e764c3cde15899e0b9bf20290ecd642bcc8/eng/MSBuild/Packaging.targets#L63 resulting in the warning:

`Microsoft.Extensions.Caching.Hybrid 9.3.0 doesn't support net481 and has not been tested with it. Consider upgrading your TargetFramework to net8.0 or later. You may also set true in the project file to ignore this warning and attempt to run in this unsupported configuration at your own risk.`

### Reproduction Steps

- Create an empty project targetting a .NET Framework version
- Add Microsoft.Extensions.Caching.Hybrid 9.3.0
- Build

```

net481

```

### Expected behavior

No warning during build

### Actual behavior

Warning is shown

### Regression?

_No response_

### Known Workarounds

```
true
```

### Configuration

- .NET Framework 4.8, 4.8.1
- Microsoft.Extensions.Caching.Hybrid 9.3.0

### Other information

https://learn.microsoft.com/en-us/aspnet/core/performance/caching/overview?view=aspnetcore-9.0#compatibility

`The HybridCache library supports older .NET runtimes, down to .NET Framework 4.7.2 and .NET Standard 2.0.`