[FIX] product_email_template: use correct parameter for notification layout

Message post with template has to be called with a notif_layout parameter in
order to have a layouting correctly set through the call chain.

closes odoo/odoo#48359

X-original-commit: 077f58027e29a50cd9a9bf455b5ca5c482503686
Signed-off-by: Thibault Delavallee (tde) <tde@openerp.com>

addons/product_email_template/models/account_move.py

@@ -14,8 +14,10 @@ class AccountMove(models.Model):
                 invoice.message_subscribe([invoice.partner_id.id])
             for line in invoice.invoice_line_ids:
                 if line.product_id.email_template_id:
-                    invoice.with_context(custom_layout="mail.mail_notification_light").message_post_with_template(
-                        line.product_id.email_template_id.id, composition_mode="comment"
+                    invoice.message_post_with_template(
+                        line.product_id.email_template_id.id,
+                        composition_mode="comment",
+                        email_layout_xmlid="mail.mail_notification_light"
                     )
         return True