VS: allowStaleResults is hardcoded false

In Editor, `ParseAndCheckDocument` extension method has only one single call site:
https://github.com/dotnet/fsharp/blame/ec08a4c7f856bb965b2bb67bb039b898d0e59268/vsintegration/src/FSharp.Editor/LanguageService/WorkspaceExtensions.fs#L207

`allowStaleResults` is false here, which means these options have no effect:

For context, this feature was introduced in #2315, but it looks like it has been defunct for quite some time now.

This is not high priority issue, but we should probably either chuck away the code path, along with the not working user options or re-enable this?