Deserialising array from `Value` allows extraneous values

The following should fail as the array is of length two but three elements are provided.

```rust
let err = Value::Seq(vec![
        Value::Number(Number::new(1)),
        Value::Number(Number::new(2)),
        Value::Number(Number::new(3)),
    ])
    .into_rust::<[i32; 2]>()
    .unwrap_err();
```

However, deserialising succeeds.