[FIX] stock: correct field reference in stock report template

Issue:
- when attempting to download the Picking Operations report for a
product with packaging, the report generation fails with an error.

Steps to Reproduce:
- Configure a product to include packaging details.
- Create a new quotation with the packaged product, and confirm it.
- Proceed to validate the delivery.
- In actions click on 'Print' > 'Picking Operations'.
- Notice the error.

Solution:
- Update the field product_packaging_quantity to the correct field name
product_packaging_qty.

OPW-3643483

closes odoo#147692

Signed-off-by: William Henrotin (whe) <whe@odoo.com>

addons/stock/report/report_stockpicking_operations.xml

@@ -122,7 +122,7 @@
                                                     (<span t-field="ml.product_packaging_qty" t-options='{"widget": "integer"}'/> <span t-field="ml.move_id.product_packaging_id.name"/>)
                                                 </span>
                                                 <span t-if="o.state == 'done'">
-                                                    (<span t-field="ml.product_packaging_quantity" t-options='{"widget": "integer"}'/> <span t-field="ml.move_id.product_packaging_id.name"/>)
+                                                    (<span t-field="ml.product_packaging_qty" t-options='{"widget": "integer"}'/> <span t-field="ml.move_id.product_packaging_id.name"/>)
                                                 </span>
                                             </span>
                                         </td>