[UPDATE] Raise PHP dependecy to 7.2

This change is non-breaking, since the lowest required version of typo3/cms-core also requires PHP 7.2

Author: vertexvaar

composer.json

@@ -11,7 +11,7 @@
     ],
     "minimum-stability": "stable",
     "require": {
-        "php": "^5.6 || ^7.0",
+        "php": "^7.2",
         "ext-openssl": "*",
         "typo3/cms-core": "^9.5 || ^10.0"
     },