[8.16](backport #4546) Link to serverless docs from main obs guide (#…

…4570)

* Link to serverless docs from main obs guide (#4546)

* Link to serverless docs from main obs guide

* Tweak wording

* Add link from serverless to stateful docs

(cherry picked from commit cbc468c)

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Co-authored-by: DeDe Morton <[email protected]>
Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>