Update PHP version to 7.4

Author: sebastianfeldmann

README.md

@@ -1,5 +1,5 @@
 [![Latest Stable Version](https://poser.pugx.org/captainhook/captainhook/v/stable.svg?v=1)](https://packagist.org/packages/captainhook/captainhook)
-[![Minimum PHP Version](https://img.shields.io/badge/php-%3E%3D%207.2-8892BF.svg)](https://php.net/)
+[![Minimum PHP Version](https://img.shields.io/badge/php-%3E%3D%207.4-8892BF.svg)](https://php.net/)
 [![Downloads](https://img.shields.io/packagist/dt/captainhook/captainhook.svg?v1)](https://packagist.org/packages/captainhook/captainhook)
 [![License](https://poser.pugx.org/captainhook/captainhook/license.svg?v=1)](https://packagist.org/packages/captainhook/captainhook)
 [![Build Status](https://github.com/captainhookphp/captainhook/workflows/Continuous%20Integration/badge.svg)](https://github.com/captainhookphp/captainhook/actions)