Assignment of lambda to delegate fails for value type with generic NRT

**Version Used**: 3.8.0-2.20408.4

**Steps to Reproduce**:

```
delegate void D<T>(out T? value);
D<int> d = (out int v) => v = 0;
```

**Expected Behavior**:

No warnings.

**Actual Behavior**:

> Warning CS8622: Nullability of reference types in type of parameter 'v' of 'lambda expression' doesn't match the target delegate D\<int>'