[FIX] pos_restaurant: make sure split bill product list is scrollable

Current behavior:
When the list of order line is too long in the split bill screen there
was no scroll bar to see the last order lines.

Steps to reproduce:
- Open PoS restaurant
- Create a new order
- Add a lot of order lines
- Click on the split bill button
- The list of order lines is not scrollable

opw-3676165

closes odoo/odoo#149800

Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>

addons/pos_restaurant/static/src/app/split_bill_screen/split_bill_screen.xml

@@ -15,7 +15,7 @@
                 </div>
 
                 <div t-if="newOrder" class="main d-flex flex-nowrap flex-grow-1 overflow-hidden">
-                    <div class="flex-grow-1 mw-50 m-3 bg-view border rounded w-50">
+                    <div class="flex-grow-1 mw-50 m-3 bg-view border rounded w-50 overflow-auto">
                         <OrderWidget lines="orderlines" t-slot-scope="scope">
                             <t t-set="line" t-value="scope.line" />
                             <Orderline line="getLineData(line)"