Deserialising array from `Value` allows extraneous values

[juntyr]

The following should fail as the array is of length two but three elements are provided.

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.