[FIX] sale_invoice_plan: fix duplicate Create Invoice button

When installed along with sale_subscription,
recurring order would show two "Create Invoice" buttons.

This is because the Subscription app adds a "Create Invoice"
button specific for recurring orders.

The solution is to not force the Sales Order original "Create Invoice"
button visible. Instead make the "Create Invoice By Plan" button
available.

sale_invoice_plan/models/sale.py

@@ -50,7 +50,6 @@ def _compute_invoice_plan_process(self):
                 and has_invoice_plan
                 and to_invoice
                 and rec.invoice_status in ["to invoice", "no"]
-                and "advance" in to_invoice.mapped("invoice_type")
             )
 
     @api.constrains("invoice_plan_ids")

sale_invoice_plan/views/sale_view.xml

@@ -88,22 +88,6 @@
                     attrs="{'invisible': [('invoice_plan_process', '=', False)]}"
                 />
             </xpath>
-            <xpath
-                expr="//button[@name='%(sale.action_view_sale_advance_payment_inv)d'][1]"
-                position="attributes"
-            >
-                <attribute
-                    name="attrs"
-                >{'invisible': ['|', ('invoice_plan_process', '=', True), ('invoice_status', '!=', 'to invoice')]}</attribute>
-            </xpath>
-            <xpath
-                expr="//button[@name='%(sale.action_view_sale_advance_payment_inv)d'][2]"
-                position="attributes"
-            >
-                <attribute
-                    name="attrs"
-                >{'invisible': ['|', ('invoice_plan_process', '=', True), '|', ('invoice_status', '!=', 'no'), ('state', '!=', 'sale')]}</attribute>
-            </xpath>
             <xpath expr="/form/sheet/notebook/page" position="after">
                 <page
                     string="Invoice Plan"