gha: add L12 to integration tests too

Author: mfn

.github/workflows/integration_tests.yml

@@ -26,7 +26,7 @@ jobs:
       fail-fast: false
       matrix:
         php: [8.2, 8.3, 8.4]
-        laravel: [^11.0]
+        laravel: [^11.0, ^12.0]
     name: P=${{ matrix.php }} L=${{ matrix.laravel }}
     runs-on: ubuntu-latest
     env: