Fix typo in 0.4 devlog: class dispatching.

[Yarwin]

[Edit bromeon]:
Closes godot-rust/gdext#1359

It should be:

let simple_dispatch: i32 = match_class! { event,
    button @ InputEventMouseButton => 1,
    motion @ InputEventMouseMotion => 2,
    action @ InputEventAction => 3,
    _ => 0,  // Fallback.
};

Instead of

let simple_dispatch: i32 = match_class!(event, {
    button @ InputEventMouseButton => 1,
    motion @ InputEventMouseMotion => 2,
    action @ InputEventAction => 3,
    _ => 0,  // Fallback.
});

[Bromeon]

Thank you!