[Contributing] consistent headlines
minor #3828 [Contributing] consistent headlines (xabbuh)

This PR was merged into the 2.3 branch.

Discussion
----------

[Contributing] consistent headlines

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

This is a follow-up of #3765.

Commits
-------

6e6601a [Contributing] consistent headlines