[FIX] project: Settings" in administration for a user

Used case:
-go as admin and set for the demo user the right "Settings" in administration
-connect as demo user, go in settings of project and untick the forecasts option and save

Result:
-Access rights error because the user has no rights to unlink records on "ir.values" model.

Fix:
When the user is in the group_system group, he has the rights to unlink records in "ir.values" model.

opw:676714