It_builds_successfully_when_targeting_net_framework test wants to compile a .NETCoreApp template on .NET Framework

[ViktorHofer]

The test It_builds_successfully_when_targeting_net_framework uses the dotnet wpf template which uses Nullable, ImplicitUsings and file scoped namespaces and tries to compile it for .NET Framework. At some point, that was successful as those templates didn't use any of these new language features but that isn't true anymore.

I'm disabling the test to unblock dependency flow in #29800 until we decide what to do with it.