Merge pull request #516 from defuse/bump-php-sec-ver

Correct the minimum security-supported PHP version in the README

README.md

@@ -15,7 +15,7 @@ This is a library for encrypting data with a key or password in PHP. **It
 requires PHP 5.6 or newer and OpenSSL 1.0.1 or newer.** We recommend using a
 version of PHP that [still has security
 support](https://www.php.net/supported-versions.php), which at the time of
-writing means PHP 7.4 or later. Using this library with an unsupported
+writing means PHP 8.0 or later. Using this library with an unsupported
 version of PHP could lead to security vulnerabilities.
 
 The current version of `php-encryption` is v2.3.1. This library is expected to