Remove explicit reference to System.ValueTuple.
Remove explicit reference to System.ValueTuple.

KirillOsenkov/SourceBrowser,akrisiun/SourceBrowser,akrisiun/SourceBrowser,KirillOsenkov/SourceBrowser,akrisiun/SourceBrowser,KirillOsenkov/SourceBrowser,akrisiun/SourceBrowser,KirillOsenkov/SourceBrowser