[FIX] point_of_sale: proxy_ip validation error at demo data loading

The demo data of point_of_sale module was failing to load when pos_iot
module was installed due to proxy_ip validation error. In fact, the iot
module overrides this field by creating a relationship to iot_ip.
When the demo data is created in the pos, the iot does not yet exist,
so proxy_ip is empty, so it trigger the validation error.

Error validation is triggered only when proxy_ip is empty and
printer_type is set to "iot". In the point_of_sale data demos, we set
printer_type to false, which fixes the problem.

closes odoo/odoo#140457

X-original-commit: 2f1af3a39b0d61dbf7c70e4fbc6421af906854d0
Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>
Signed-off-by: David Monnom (moda) <moda@odoo.com>

addons/point_of_sale/data/point_of_sale_demo.xml

@@ -66,6 +66,7 @@
             <field name="name">Preparation Printer</field>
             <field name="proxy_ip">localhost</field>
             <field name="product_categories_ids" eval="[(6, 0, [ref('point_of_sale.pos_category_miscellaneous')])]" />
+            <field name="printer_type" eval="False" />
         </record>
 
         <!-- Taxes -->