Call the correct API to determine if a user is in treatment or control group

[luabud]

We seem to be using isInExperimentSync but that returns whether a user is in treatment or control, but we should probably be using getTreatmentVariable? This issue is so we can figure this out.

[luabud]

It really should be getExperimentValue: https://github.com/microsoft/tas-client/tree/main/vscode-tas-client#use

[karrtikr]

Great, we don't have an issue tracking implementing this though, so can we reopen this?

[luabud]

Oops, good point :) thank you!