Resolving to-dos nullifies their `snoozed_until` column

What does this MR do and why?

Resolving to-dos nullifies their snoozed_until column

We don't need to retain snooze data on resolved to-dos.

SQL queries

TodoService.resolve_todo

https://console.postgres.ai/gitlab/gitlab-production-main/sessions/36053/commands/111191

UPDATE
    "todos"
SET
    "state" = 'done',
    "updated_at" = '2025-02-07 14:05:19.138128',
    "resolved_by_action" = 0,
    "snoozed_until" = NULL
WHERE
    "todos"."id" = 22

TodoService.resolve_todos

https://console.postgres.ai/gitlab/gitlab-production-main/sessions/36053/commands/111192

UPDATE
    "todos"
SET
    "state" = 'done',
    "resolved_by_action" = 0,
    "snoozed_until" = NULL,
    "updated_at" = '2025-02-07 14:10:29.056655'
WHERE (user_id = 1
    AND state = 'pending')
AND "todos"."id" IN (
    SELECT
        "todos"."id"
    FROM
        "todos"
    WHERE (user_id = 1
        AND state = 'pending'))
AND "todos"."state" != 'done'

References

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MR acceptance checklist

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How to set up and validate locally

1. Navigate to the to-dos dashboard at https://gdk.test:3443/dashboard/todos.
2. Snooze some to-dos.
3. Navigate to the Snoozed tab.
4. Resolve some to-dos.
5. Navigate to the Done tab.
   • The to-do you just resolved should not have a Snoozed until... label.

Related to #17712 (closed)