message: Fix db_scan documentation
diff: @@ -95,7 +95,8 @@ where
  // Creates an iterator that will go from start to end
  // Order is defined in cosmwasm::traits::Order and may be 1/Ascending or 2/Descending.
  // Ownership of both start and end pointer is not transferred to the host.
  - // Returns negative code on error, 0 on success
  + // Returns negative code on error.
  + // Returns iterator ID > 0 on success.
  "db_scan" => Func::new(move |ctx: &mut Ctx, start_ptr: u32, end_ptr: u32, order: i32| -> i32 {
  do_scan::<S, Q>(ctx, start_ptr, end_ptr, order)
  }),
  