[IMP] purchase: create&edit for Payment Terms

If a user is at the same time purchase user and billing manager
he can't create a new payment terms from the PO and he has to
navigates throws multiple menus instead of just using the create
and edit function.

taskId 1868555
Closes #28280

addons/purchase/views/purchase_views.xml

@@ -261,7 +261,7 @@
                                 <group>
                                     <field name="user_id"/>
                                     <field name="invoice_status"/>
-                                    <field name="payment_term_id" options="{'no_open': True, 'no_create': True}" attrs="{'readonly': ['|', ('invoice_status','=', 'invoiced'), ('state', '=', 'done')]}"/>
+                                    <field name="payment_term_id" attrs="{'readonly': ['|', ('invoice_status','=', 'invoiced'), ('state', '=', 'done')]}"/>
                                     <field name="fiscal_position_id" options="{'no_create': True}" attrs="{'readonly': ['|', ('invoice_status','=', 'invoiced'), ('state', '=', 'done')]}"/>
                                     <field name="date_approve" groups="base.group_no_one"/>
                                 </group>