Fix shorthand field pat for destructure_tuple_binding

[A4-Tacks]

Example

struct S { field: (i32, i32) }
fn main() {
    let S { $0field } = S { field: (2, 3) };
    let v = field.0 + field.1;
}

Before this PR:

struct S { field: (i32, i32) }
fn main() {
    let S { ($0_0, _1) } = S { field: (2, 3) };
    let v = _0 + _1;
}

After this PR:

struct S { field: (i32, i32) }
fn main() {
    let S { field: ($0_0, _1) } = S { field: (2, 3) };
    let v = _0 + _1;
}