Put agent field in sale form on a new line

This prevents to break the layout of other modules adding fields to the same
tab.

Closes #14934
(grafted from f9fb03a42e7c55c33072181b0ec48ac5469495f1)

--HG--
branch : 8.0

modules/commission/view/sale_form.xml

@@ -2,9 +2,9 @@
 <!-- This file is part of Tryton.  The COPYRIGHT file at the top level of
 this repository contains the full copyright notices and license terms. -->
 <data>
-    <xpath expr="/form/notebook/page[@id='other']/field[@name='company']"
-        position="after">
+    <xpath expr="//page[@id='other']/field[@name='origin']" position="after">
         <label name="agent"/>
         <field name="agent"/>
+        <newline/>
     </xpath>
 </data>