SourceLink doesn't work with the Microsoft.ML NuGet package

[eerhardt]

System information

• OS version/distro: Windows
• .NET Version (eg., dotnet --info): net471

Issue

• What did you do?
  Debug an application that uses Microsoft.ML.
  Load the symbols from the public Microsoft symbols server.
  Try to F11 into new LearningPipeline();.

• What happened?
  Visual Studio prompted me to find the LearningPipeline.cs file myself.

• What did you expect?
  I expected Visual Studio to automatically download the file from GitHub for me and step into it.