[FIX] maintenance: restrict deletion of teams related to equipment

Currently, an error occurs when the user follows the below steps and tries to
run cron "Maintenance: generate preventive maintenance requests"

Steps:
- Open maintenance > Configuration > Maintenence Teams
- Create new team e.g. "ABC"
- Go to Equipments and create new equipemnt
- Set 1 "Preventive Maintenance Frequency" from maintenance page
- Select "ABC" in Maintenance Team >> save it
- Delete  Maintenence Team "ABC"

This commit solves the above issue by restricting the deletion
of maintenance teams who are related to equipment.

sentry-4467657509

closes odoo/odoo#137943

X-original-commit: 9e4aa20c05999ccd9952480b8fea22b9fb651d74
Signed-off-by: Tiffany Chang (tic) <tic@odoo.com>
Signed-off-by: ANSARI MAHAMADASIF (maan) <maan@odoo.com>

addons/maintenance/models/maintenance.py

@@ -131,7 +131,7 @@ class MaintenanceEquipment(models.Model):
     maintenance_open_count = fields.Integer(compute='_compute_maintenance_count', string="Current Maintenance", store=True)
     period = fields.Integer('Days between each preventive maintenance')
     next_action_date = fields.Date(compute='_compute_next_maintenance', string='Date of the next preventive maintenance', store=True)
-    maintenance_team_id = fields.Many2one('maintenance.team', string='Maintenance Team', check_company=True)
+    maintenance_team_id = fields.Many2one('maintenance.team', string='Maintenance Team', check_company=True, ondelete="restrict")
     maintenance_duration = fields.Float(help="Maintenance Duration in hours.")
 
     @api.depends('effective_date', 'period', 'maintenance_ids.request_date', 'maintenance_ids.close_date')