Clarify that you can't expect the redaction of a state event to remove its effect.

Link to problem area:

Possibly other areas too but the most obvious one to me would be the following:

https://github.com/matrix-org/matrix-spec/blob/a2027a398541552b31572c948e7b6bdd2a802adf/content/client-server-api/_index.md?plain=1#L3180-L3186

Issue

This came up whilst implementing spaces on Element X. The spec suggests that children can be removed from spaces via redaction, but Element Web doesn't support this and expects empty m.space.child/parent events to be sent instead. Following further discussion, @dkasak summarised the issue like so:

⁦In my mind, redactions have one and only one purpose: to redact information meant for consumption by other humans from a message. They should never be used for anything that could have an effect, such as removing any kind of authorization data.

⁦It was also always my impression that they were never designed for any other purpose than removing human level information?

It's not that you shouldn't redact state events, that's an entirely valid thing to do. It's that you shouldn't expect that redacting a state event is going to somehow remove its effect.⁦

Start with the referenced sections in content/client-server-api/_index.md and content/client-server-api/modules/spaces.md, then search for other wording about removing space children via redaction. Clarify that redacting a state event does not necessarily remove its effect, and make the expected alternative behavior unambiguous. Done means the specification no longer suggests redaction alone removes a child from a space.