Drop support for PHP < 7.4

Author: mmoll

composer.json

@@ -22,7 +22,7 @@
         "source": "https://github.com/mayflower/mo4-coding-standard"
     },
     "require": {
-        "php": "~7.2 || ~8.0",
+        "php": "~7.4 || ~8.0",
         "dealerdirect/phpcodesniffer-composer-installer": "~0.7",
         "escapestudios/symfony2-coding-standard": "^3.10.0",
         "slevomat/coding-standard": "^7.0.1",