remove Knp RAD Components link (dead)

README.md

 *Extras related to web development frameworks.*
 
 * [CakePHP CRUD](https://github.com/friendsofcake/crud) - A Rapid Application Development (RAD) plugin for CakePHP.
-* [Knp RAD Components](https://rad.knplabs.com/) - A set of Rapid Application Development (RAD) components for Symfony.
 * [LaravelS](https://github.com/hhxsv5/laravel-s) - An out-of-the-box adapter between Laravel/Lumen and Swoole.
 * [Livewire](https://livewire.laravel.com/) - Powerful, dynamic, front-end UIs without leaving PHP.