[FIX] web: Form: right align subtotals

The subtotals displayed in the oe_subtotal_footer (e.g. sale.order
form view) should be right aligned. Before this rev. this wasn't
the case for monetary fields, they are now displayed 'inline-flex',
whatever the form mode (before the new views, they were
'inline-flex' only in edit mode).

Credit goes to @qsm-odoo.

addons/web/static/src/less/form_view.less

@@ -435,6 +435,7 @@
 
             .o_field_widget {
                 text-align: right;
+                .o-justify-content(flex-end);
                 width: 100%;
             }
         }