fix(recurrence): drop the now-unused child binding

The spawn's explicit embed call went with #280 step 3; the create_note result
had no other reader.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UaYUaouG9jjhATyuxCKrQs

src/scribe/services/recurrence.py

@@ -125,7 +125,7 @@ async def spawn_recurring_tasks() -> int:
         base_date = task.due_date or now.date()
         next_due = calculate_next_due(task.recurrence_rule, base_date)
         try:
-            child = await create_note(
+            await create_note(
                 task.user_id,
                 title=task.title,
                 body=task.body or "",