Readd basetargets in Microsoft.ML.OnnxRuntime.csproj (#18789)
### Description
<!-- Describe your changes. -->
### Motivation and Context
Now, the nightly Microsoft.ML.Onnxruntime.Managed Nuget Packag couldn't
be added in dotnet console program in VS2022 with target framework .NET
6.0.
I just restore it to previous setting to make it work.