What does this PR do?

Include /health into OpenAPI doc

Before submitting

• [x] This PR fixes a typo or improves the docs (you can dismiss the other checks if that's the case).
• [x] Did you read the contributor guideline, Pull Request section?
• [ ] Was this discussed/approved via a Github issue or the forum? Please add a link to it if that's the case.
• [x] Did you make sure to update the documentation with your changes? Here are the documentation guidelines, and here are tips on formatting docstrings.
• [ ] Did you write any new necessary tests?

Who can review?

@OlivierDehaene OR @Narsil

Hi @OlivierDehaene , do you have any concern about updating the OpenAPI doc? I think this PR is low-risky.