mistakenly failed to remove `approved` after requirements changed

I originally filed https://github.com/kubernetes/enhancements/pull/5923 as a sig-network KEP, and so [it got `approved`](https://github.com/kubernetes/enhancements/pull/5923#issuecomment-3908889087) because I'm a sig-network approver. When I repushed it as a sig-architecture KEP, [the bot said](https://github.com/kubernetes/enhancements/pull/5923#issuecomment-5453924514):

> [APPROVALNOTIFIER] This PR is APPROVED
>
> Approval requirements bypassed by manually added approval.
>
> This pull-request has been approved by: *danwinship*

which is incorrect; my `keps/sig-network/` approval is no good on a PR against `keps/sig-architecture/`

Start with the approval-notifier behavior described for Kubernetes enhancements PR #5923, where a manually added approval remains valid after the KEP moves from sig-network to sig-architecture. No source file or test is named in the issue; trace the approval handling and define done as removing or invalidating the approval when the target area changes.

Written by the indexing model from the issue text.