Possibly Missing Interpolation in SMTLibInteractiveTheoremProver

Hi,
I was reading the source code of the SMTLibInteractiveTheoremProver class, and I saw that line 812 has the following context:
```csharp
foreach (var relaxVar in relaxVars)
{
  var resp = await SendVcRequest("(get-value ({relaxVar}))").WaitAsync(cancellationToken);
...
```
I saw this as highly suspicious, prompting me to open this issue. Should there not be a $ before `"(get-value...`?
