DOC: `doxygenfunction` is not working in development documentation

### Issue with current documentation:

In the [How to contribute documentation](https://numpy.org/doc/stable/dev/howto-docs.html#writing-the-comment-blocks), some doxygen examples emit `doxygenfunction: Unable to resolve function` warnings and do not output the documentation as expected.

### Idea or request for content:

_No response_