TryComputeClrArgumentType doesn't do anything

https://github.com/pythonnet/pythonnet/blob/de7a1d2d2aa505a4be5e4dee9368e514b6963bef/src/runtime/MethodBinder.cs#L691-L693

Was stepping through the code trying to debug something (I think) unrelated, and noticed that `TryComputeClrArgumentType` always skips its contents. Is that intended? 