[FIX] point_of_sale: prevent trackback when changing journal in report.pos.order

This issue occurs when the user changes the Journal 'journal_id' in this
'report.pos.order' model then traceback will be generated.

Step to Produce:-
- In POS, Click on Reporting Menu > Order.
- Click on graph > Open any One record.
- Try To Change the Journal('journal_id').
- Trace-back will be generated.

sentry:- 3929247828

closes odoo/odoo#118660

X-original-commit: 87ed00e65ecaa22c559a43452c87d4f16e598f3f
Signed-off-by: Joseph Caburnay (jcb) <jcb@odoo.com>

addons/point_of_sale/report/pos_order_report.py

@@ -18,7 +18,7 @@ class PosOrderReport(models.Model):
     state = fields.Selection(
         [('draft', 'New'), ('paid', 'Paid'), ('done', 'Posted'),
          ('invoiced', 'Invoiced'), ('cancel', 'Cancelled')],
-        string='Status')
+        string='Status', readonly=True)
     user_id = fields.Many2one('res.users', string='User', readonly=True)
     price_total = fields.Float(string='Total Price', readonly=True)
     price_sub_total = fields.Float(string='Subtotal w/o discount', readonly=True)
@@ -27,8 +27,8 @@ class PosOrderReport(models.Model):
     company_id = fields.Many2one('res.company', string='Company', readonly=True)
     nbr_lines = fields.Integer(string='Sale Line Count', readonly=True)
     product_qty = fields.Integer(string='Product Quantity', readonly=True)
-    journal_id = fields.Many2one('account.journal', string='Journal')
-    delay_validation = fields.Integer(string='Delay Validation')
+    journal_id = fields.Many2one('account.journal', string='Journal', readonly=True)
+    delay_validation = fields.Integer(string='Delay Validation', readonly=True)
     product_categ_id = fields.Many2one('product.category', string='Product Category', readonly=True)
     invoiced = fields.Boolean(readonly=True)
     config_id = fields.Many2one('pos.config', string='Point of Sale', readonly=True)