update readme

Author: flc1125

README.md

@@ -2,7 +2,6 @@
 
 [![Latest Stable Version](https://poser.pugx.org/flc/laravel-middleware-cache-response/v/stable)](https://packagist.org/packages/flc/laravel-middleware-cache-response)
 [![Total Downloads](https://poser.pugx.org/flc/laravel-middleware-cache-response/downloads)](https://packagist.org/packages/flc/laravel-middleware-cache-response)
-![php>=5.4](https://img.shields.io/badge/php->%3D5.4-orange.svg?maxAge=2592000)
 [![License](https://poser.pugx.org/flc/laravel-middleware-cache-response/license)](https://packagist.org/packages/flc/laravel-middleware-cache-response)
 
 ## 功能