[chore] Move messaging attribute footnotes to yaml

[thompson-tomo]

Changes

This moves a couple of attribute notes for kafka/rocketmq from being freetext markdown to be notes in the yaml and generated,

No changes in content have been done.

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Merge requirement checklist

• [x] CONTRIBUTING.md guidelines followed.
• [ ] Change log entry added, according to the guidelines in When to add a changelog entry.
  • If your PR does not need a change log, start the PR title with [chore]
• [ ] Links to the prototypes or existing instrumentations (when adding or changing conventions)