[FIX] gamification: trace-back in goals history

Hello,

I have fixed the traceback : Traceback that comes when opens the Goals History from the menu Human Resources -> Engagement -> Goals History. and hide create button on "Goal History" menu.

More details:

- Task : https://www.odoo.com/web#id=9163&view_type=form&model=project.task&menu_id=3942&action=327
- Pad : https://pad.odoo.com/p/openerp-project.task-34TKRIJUHI

Thanks,
cod-odoo