bug #1861 Fix InvoiceCreator demo (WebMamba)

This PR was merged into the 2.x branch.

Discussion
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Fix InvoiceCreator demo

| Q             | A
| ------------- | ---
| Bug fix?      | yes
| New feature?  | no
| Issues        | Fix slack: https://symfony-devs.slack.com/archives/C01FN4EQNLX/p1716282168599679
| License       | MIT

Looks like a regression occurred in #[LiveArg]. I need to dig more on this but let's fix that first

Commits
-------

1e23d94 Fix InvoiceCreator demo

Author: kbond

ux.symfony.com/src/Twig/InvoiceCreator.php

@@ -83,14 +83,14 @@ public function onLineItemEditModeChange(#[LiveArg] int $key, #[LiveArg] $isEdit
     }
 
     #[LiveListener('line_item:save')]
-    public function saveLineItem(#[LiveArg] int $key, #[LiveArg] Product $product, #[LiveArg] int $quantity): void
+    public function saveLineItem(#[LiveArg] int $key, #[LiveArg] int $product, #[LiveArg] int $quantity): void
     {
         if (!isset($this->lineItems[$key])) {
             // shouldn't happen
             return;
         }
 
-        $this->lineItems[$key]['productId'] = $product->getId();
+        $this->lineItems[$key]['productId'] = $product;
         $this->lineItems[$key]['quantity'] = $quantity;
     }