Update code after moonbit bugs fixed

[bikallem]

1. Remove default value in optional args
   • https://github.com/bikallem/webapi/tree/remove-default-value,
   • ICE: Key_not_found in link-core when optional Array[T] parameter has no default value (JS target) moonbitlang/moonbit-docs#1133
2. Remove redundant to_js from traits after empty traits issue is fixed
   • https://github.com/bikallem/mbt-ffi/blob/main/dom/event_target.mbt#L34
   • Empty traits allow coercion from any type to trait object, bypassing nominal check moonbitlang/moonbit-docs#1129