[wasm-js-api-1] Align with Web IDL specification

Author: autokagami

document/js-api/index.bs

@@ -726,7 +726,7 @@ interface Table {
   constructor(TableDescriptor descriptor);
   unsigned long grow([EnforceRange] unsigned long delta);
   Function? get([EnforceRange] unsigned long index);
-  void set([EnforceRange] unsigned long index, Function? value);
+  undefined set([EnforceRange] unsigned long index, Function? value);
   readonly attribute unsigned long length;
 };
 </pre>