[FIX] point_of_sale: recursive pos.category error message

Instead of showing a traceback, show a user-friendly error message
to the user to avoid recursive pos.category.

closes odoo/odoo#38769

Signed-off-by: pimodoo <pimodoo@users.noreply.github.com>

addons/point_of_sale/models/pos_category.py

 # -*- coding: utf-8 -*-
 # Part of Odoo. See LICENSE file for full copyright and licensing details.
 from odoo import api, fields, models, _
+from odoo.exceptions import ValidationError
 
 
 class PosCategory(models.Model):
@@ -11,7 +12,7 @@ class PosCategory(models.Model):
     @api.constrains('parent_id')
     def _check_category_recursion(self):
         if not self._check_recursion():
-            raise ValueError(_('Error ! You cannot create recursive categories.'))
+            raise ValidationError(_('Error ! You cannot create recursive categories.'))
 
     name = fields.Char(string='Category Name', required=True, translate=True)
     parent_id = fields.Many2one('pos.category', string='Parent Category', index=True)