[FIX] base: rendering PDF should save ir.attachment

Printing an invoice no longer saved the ir.attachment on the
move.
This is due to the refactor in ffc525419a,
since the render methods are now `api.model`, `self.attachment` was always
Falsy. To get the attachment name of a report, we need to call
`self._get_report(report_ref)`.

closes odoo/odoo#100363

Signed-off-by: Laurent Smet <las@odoo.com>

odoo/addons/base/models/ir_actions_report.py

@@ -799,7 +799,7 @@ class IrActionsReport(models.Model):
         report_sudo = self._get_report(report_ref)
 
         # Generate the ir.attachment if needed.
-        if self.attachment:
+        if report_sudo.attachment:
             attachment_vals_list = []
             for res_id, stream_data in collected_streams.items():
                 # An attachment already exists.