TASK: Raise minimum PHP to 7.4

… as typed class properties are used in the code.

Author: kdambekalns

composer.json

@@ -5,7 +5,7 @@
     "homepage": "http://flowpack.org/",
     "license": ["LGPL-3.0-only"],
     "require": {
-        "php": "^7.3 || ^8.0",
+        "php": "^7.4 || ^8.0",
         "ext-json": "*",
 
         "flowpack/elasticsearch": "^5.0 || dev-master",