Remove Radar

Doesn't seem to be maintained.

README.md

 
 * [Laravel-Zero](https://laravel-zero.com) - A micro-framework for console applications.
 * [Mezzio](https://getexpressive.org/) - A micro-framework by Laminas.
-* [Radar](https://github.com/radarphp/Radar.Adr) - An Action-Domain-Responder implementation for PHP.
 * [Silly](https://github.com/mnapoli/silly) - A micro-framework for CLI applications.
 * [Slim](https://www.slimframework.com/) - Another simple micro framework.