[FIX] hr: don't use .write() in a computed method

Before this commit, the computed field _compute_is_system make a write which
one is a bad practice and trigger a lot of others calls on res.user model.

opw-2716468

closes odoo/odoo#81555

X-original-commit: f85a67935c5dfa660e94f9bed8e8058c8df256cc
Signed-off-by: Jérémy Kersten <jke@odoo.com>

addons/hr/models/res_users.py

@@ -137,7 +137,7 @@ class User(models.Model):
 
     @api.depends_context('uid')
     def _compute_is_system(self):
-        self.write({'is_system': self.env.user._is_system()})
+        self.is_system = self.env.user._is_system()
 
     def _compute_can_edit(self):
         can_edit = self.env['ir.config_parameter'].sudo().get_param('hr.hr_employee_self_edit') or self.env.user.has_group('hr.group_hr_user')