Remove source-build prebuilt detection from fsharp

[MichaelSimons]

See #5034 for details

• Remove eng/SourceBuildPrebuiltBaseline.xml if one exists
• Remove all source build intermediate dependencies in Version.Details.xml

This should only be done on branches that do not flow into a 9.0 SDK. If the branch flows into a 9.0 SDK, these changes must wait.

[ViktorHofer]

dotnet/fsharp#18535