[FIX] stock: use proper font in PDF report

When printing a delivery order in waiting state under MS Windows, the
produced PDF does not use the proper font for the warning line.
This leads to an unreadable line full of small rectangles.

The problem comes from the fact that the 'fa' class is applied to a full
paragraph.

With this commit, the proper 'i' tag is used to display the exclamation
triangle.

opw-1931892

closes odoo/odoo#30680

addons/stock/report/report_stockpicking_operations.xml

@@ -155,7 +155,7 @@
                                 </tbody>
                             </table>
                             <t t-set="no_reserved_product" t-value="o.move_lines.filtered(lambda x: x.product_uom_qty != x.reserved_availability and x.move_line_ids and x.state!='done')"/>
-                            <p t-if="o.state in ['draft', 'waiting', 'confirmed'] or no_reserved_product" class="fa fa-exclamation-triangle">
+                            <p t-if="o.state in ['draft', 'waiting', 'confirmed'] or no_reserved_product"><i class="fa fa-exclamation-triangle" />
                                 All products could not be reserved. Click on the "Check Availability" button to try to reserve products
                             </p>
                             <p t-field="o.note"/>