Add caveat about active feature development

What does this MR do and why?

We have a number of active work items relating to abuse features being tracked in confidential epics and issues. E.g. https://gitlab.com/groups/gitlab-org/modelops/anti-abuse/-/epics/14+.

However we receive regular H1 reports about banning "not working" or "being bypassed".

This MR gives public visibility that yes, we know there are areas still being worked on as proposed in https://gitlab.com/groups/gitlab-org/modelops/anti-abuse/-/epics/14#note_1411687615

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