if should add offset from the statrt, but not the end

- `whir\src\protocols\whir\verifier.rs` :

```rust
let start = evaluation_point.len().saturating_sub(num_variables);
```

- `evaluation_point` ：

```rust
let evaluation_point = round_folding_randomness
    .into_iter()
    .flat_map(|poly| poly.0.into_iter())
    .collect::<Vec<_>>();
```
