Remove unreferenced packages

[MichaelSimons]

More cleanup...

Removed the following packages which are not referenced by the product source-build.

1. microsoft.build.framework.15.1.1012.nupkg
2. microsoft.build.framework.15.3.409.nupkg
3. microsoft.build.framework.17.3.1.nupkg
4. microsoft.build.traversal.3.1.6.nupkg
5. microsoft.build.utilities.core.16.11.0.nupkg
6. microsoft.build.utilities.core.16.7.0.nupkg
7. microsoft.build.utilities.core.17.5.0.nupkg
8. microsoft.codeanalysis.csharp.4.4.0.nupkg
9. microsoft.codeanalysis.csharp.workspaces.4.5.0.nupkg
10. microsoft.codeanalysis.visualbasic.4.4.0.nupkg
11. microsoft.codeanalysis.visualbasic.workspaces.4.5.0.nupkg
12. microsoft.codeanalysis.workspaces.common.4.4.0.nupkg
13. microsoft.dotnet.platformabstractions.2.1.0.nupkg
14. microsoft.net.stringtools.17.3.1.nupkg
15. nuget.protocol.6.5.0.nupkg
16. system.collections.nongeneric.4.0.1.nupkg
17. system.componentmodel.composition.4.5.0.nupkg
18. system.composition.7.0.0.nupkg
19. system.console.4.0.0.nupkg
20. system.diagnostics.eventlog.7.0.0.nupkg
21. system.diagnostics.process.4.1.0.nupkg
22. system.diagnostics.stacktrace.4.3.0.nupkg
23. system.diagnostics.tools.4.0.1.nupkg
24. system.io.pipes.4.3.0.nupkg
25. system.resources.reader.4.0.0.nupkg
26. system.runtime.serialization.xml.4.1.1.nupkg
27. system.security.accesscontrol.4.3.0.nupkg
28. system.security.accesscontrol.4.5.0.nupkg
29. system.security.cryptography.protecteddata.7.0.0.nupkg
30. system.text.encoding.codepages.4.3.0.nupkg
31. system.threading.tasks.parallel.4.3.0.nupkg
32. system.threading.threadpool.4.3.0.nupkg
33. system.threading.timer.4.0.1.nupkg
34. system.valuetuple.4.3.0.nupkg
35. system.xml.xpath.xdocument.4.3.0.nupkg