Rustfmt adds new indentation every time it formats `let else` in macro declaration

Example code:

```rust
// The indentation stays the same, as expected
fn foobar() {
    let x = y else {
        panic!();
    };
}

// The indentation is increased every time you run `cargo fmt`
macro_rules! foobar {
    () => {
        let pat = expr else {
                    panic!();
                };
    };
}
```