Changes constraint from exact '7.4.13' to '^7.4.13'. The pin was
introduced for CVE-2026-48736 but is overly restrictive — any 7.4.x
release >= 7.4.13 includes the fix. This allows future security
patches to install via composer update.
Note: Symfony 8.x is blocked by laravel/framework ^12 which requires
symfony/http-foundation ^7.2.0. Symfony 8 support arrives with Laravel 13.