[IMP] improve visibility changes as per task specification

- Task: https://www.odoo.com/web#id=5183&view_type=form&model=project.task&action=333&active_id=131
- Pad: https://pad.odoo.com/p/r.osgTl7m2AJDF4CQy
I think the help is not necessary. It does not add anything to the filter.