Validate backup-utility config of agent_plan_content object storage
We should make sure that CNG is aware of this bucket and run a test that backup/restore of the functionality is working for this bucket.
The following discussion from !5029 should be addressed:
- [ ] @Alexand started a [discussion](https://gitlab.com/gitlab-org/charts/gitlab/-/merge_requests/5029#note_3352973403):
> @kivikakk, heads up that this needs to be considered in the backup-utility on a follow-up MR: https://gitlab.com/gitlab-org/build/CNG/-/blob/6702aadcb4d444e488c34d561646beef32e50b5d/gitlab-toolbox/scripts/bin/backup-utility#L19.
>
> But simply mounting this value here does not break the existing backup/restore. So, it does not block this MR.
>
> I'll open a follow-up issue for you to track this one.
issue