bug-hunting.rst: Fix an example and a typo in a Sphinx tag

- Use the same file name in the explanation and in the example (conex.c vs
sonixj.c)
- Add a missing ':' in a :ref: tag which leads to incorrect Shpinx output
- Add some missing ',' and ';'

Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>