KB review - done

Closes #2750 (closed).

This MR has no changes on purpose. The ARM part of this has been merged, and you can find it here: !2121 (merged).

This MR is about reviewing the KB article about client classification. That can be found here:

• Live: https://kb.isc.org/v1/docs/en/understanding-client-classification
• Portal: https://portal.document360.io/956e37e2-5ec0-4942-8b27-35533899f099/document/v1/view/a8a95609-736a-4472-a809-5a2809e13a30/en

Consider the suggested changes:

• the original version of the KB article: understanding-client-classification-1.txt
• the suggested version of the KB article: understanding-client-classification-2.txt
• the diff between the two above: kb-understanding-client-classification.diff

You can also diff v2 and v3 in the document360 page accessible in the portal link above, if that's more convenient.

The change to the KB article have already been applied, but I'd still like someone to take a quick look.

A second point is about moving the KB article to the ARM, but I don't know if it's worth the bother.