Add Warning for Wrong Options in `eb --confighelp`

The `[job]` section generated by `eb --confighelp` has wrong options. This has already been brought up in other issues, easybuilders/easybuild#329 or easybuilders/easybuild-framework#1331. Since they have been open for quite a while, it would be nice to have a warning/note in the documentation that informs users of the issue.