[FIX] stock: don't require lot_id on reporting/location

To Reproduce
=============
- enable multi step routes
- edit Receipts operation and uncheck the two options under Traceability
- create storable product with Traceability using lot/serial number
- make purchase of this product and receive it in your inventory
- under inventory/reports/Locations click on line of this product
you will be stuck at that page even if you click discard

Problem
=======
There is an inconsistency between the view and backend, as we allow
receiving traceable product without setting `lot_id`, but in view
require `lot_id` if tracking is enabled on product.

Solution
========
following this [comment](https://github.com/odoo/odoo/blob/16.0/addons/stock/models/stock_move_line.py#L558-L560), `lot_id` shouldn't be required on view.

opw-3422259

closes odoo/odoo#130793

X-original-commit: 768b1755909fa10c39a51c68675b7aa99c91b462
Signed-off-by: Arnold Moyaux (arm) <arm@odoo.com>
Signed-off-by: Abdelouahab Laaroussi (abla) <abla@odoo.com>

addons/stock/views/stock_quant_views.xml

@@ -135,8 +135,7 @@
                        attrs="{'readonly': [('id', '!=', False)]}"/>
                 <field name="lot_id" groups="stock.group_production_lot"
                        attrs="{
-                            'readonly': ['|', ('id', '!=', False), ('tracking', 'not in', ['serial', 'lot'])],
-                            'required': [('tracking', '!=', 'none')]
+                            'readonly': ['|', ('id', '!=', False), ('tracking', 'not in', ['serial', 'lot'])]
                        }"
                        invisible="context.get('hide_lot', False)"
                        context="{'default_product_id': product_id, 'default_company_id': company_id}"/>