docs: require PHP 7.4.3+

Author: kenjis

README.md

@@ -37,7 +37,7 @@ Usage of Shield requires the following:
 
 - A [CodeIgniter 4](https://github.com/codeigniter4/CodeIgniter4/)-based project
 - [Composer](https://getcomposer.org/) for package management
-- PHP 7.4+
+- PHP 7.4.3+
 
 ### Installation