item: display quantity instead of item_quantity in Item_viewTrackingList

Since last changes on Item_getTrackingList, we no longer have item_quantity, so the
column "Quantity" was displaying nothing. So use quantity instead.

bt5/erp5_item/SkinTemplateItem/portal_skins/erp5_item/Item_viewTrackingList.xml

@@ -92,7 +92,7 @@
                       <list>
                         <string>listbox_date</string>
                         <string>listbox_variation_category_item_list</string>
-                        <string>listbox_item_quantity</string>
+                        <string>listbox_quantity</string>
                       </list>
                     </value>
                 </item>

bt5/erp5_item/SkinTemplateItem/portal_skins/erp5_item/Item_viewTrackingList/listbox.xml

@@ -116,7 +116,7 @@
                           <string>State</string>
                         </tuple>
                         <tuple>
-                          <string>item_quantity</string>
+                          <string>quantity</string>
                           <string>Quantity</string>
                         </tuple>
                       </list>

bt5/erp5_item/SkinTemplateItem/portal_skins/erp5_item/Item_viewTrackingList/listbox_item_quantity.xml → bt5/erp5_item/SkinTemplateItem/portal_skins/erp5_item/Item_viewTrackingList/listbox_quantity.xml

@@ -14,7 +14,7 @@
         </item>
         <item>
             <key> <string>id</string> </key>
-            <value> <string>listbox_item_quantity</string> </value>
+            <value> <string>listbox_quantity</string> </value>
         </item>
         <item>
             <key> <string>message_values</string> </key>