remove category colonne (useless here)

compute_purchase_order/views/computed_purchase_order.xml

@@ -57,7 +57,6 @@
           <field name="order_line_ids" context="{'cpo_seller_id': supplier_id}">
             <tree string="Order Lines" editable='bottom'>
               <field name="product_template_id" domain="[('main_seller_id', '=', cpo_seller_id)]"/>
-              <field name="category_id" readonly='1'/>
               <field name="qty_available" readonly='1'/>
               <field name="uom_id" readonly='1'/>
               <field name="average_consumption" readonly='1'/>