apply headline guidelines to the cookbook articles
minor #4042 [Cookbook] apply headline guidelines to the cookbook articles (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
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[Cookbook] apply headline guidelines to the cookbook articles

| Q             | A
| ------------- | ---
| Doc fix?      | yes
| New docs?     | no
| Applies to    | all
| Fixed tickets |

This completes the work started in #3765, #3828 and #3829.

Commits
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1fa40f3 apply headline guidelines to the cookbook articles