Delete namespace_deletion_schedule when restoring project marked for deletion.

What does this MR do and why?

Destroy the project's deletion schedule when setting marked_for_deletion_at column to NULL. This is the next step towards moving deletion schedule related column off the projects table

DELETE Query Plan: https://console.postgres.ai/gitlab/gitlab-production-main/sessions/40046/commands/123244

References

Closes #540603 (closed)

Screenshots or screen recordings

N/A

How to set up and validate locally

1. Enable the replicate_deletion_schedule_operations feature flag Feature.enable(:replicate_deletion_schedule_operations)
2. Open a project and go to Settings > General > Advanced > Delete Project to marked the project for deletion.
3. In the rails console, run the following command to add a deletion schedule:

Project.find_by_path(...).project_namespace.deletion_schedule = Namespaces::DeletionSchedule.create!(marked_for_deletion_at: Time.current, deleting_user: User.first)

4. Go back to Settings > General > Advanced > Restore Project and restore the project.
5. Run the following command to verify that the restoration is successful:

Project.find_by_path(...).project_namespace.deletion_schedule
=> nil

Project.find_by_path(...).marked_for_deletion_at
=> nil

MR acceptance checklist

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