[FIX] payment: remove transaction from session

Sequentially previewing and paying two sale orders was causing a
redirection issue. Instead of being redirect to the SO preview
(/my/orders/<:order_id>), the user was redirected to /payment/process.

The issue was due to processed transactions not being removed from the
session.

opw-1948288
Closes #31741

Signed-off-by: Toufik Benjaa (tbe) <tbe@odoo.com>

addons/payment/controllers/portal.py

@@ -66,6 +66,10 @@ class PaymentProcessing(http.Controller):
                 'success': False,
                 'error': 'no_tx_found',
             }
+
+        processed_tx = payment_transaction_ids.filtered('is_processed')
+        self.remove_payment_transaction(processed_tx)
+
         # create the returned dictionnary
         result = {
             'success': True,