MC-40555: Add PHP 7.4 declaration

- Updated framework root composer.json

Author: svera

lib/internal/Magento/Framework/composer.json

@@ -10,7 +10,7 @@
         "sort-packages": true
     },
     "require": {
-        "php": "~7.3.0",
+        "php": "~7.3.0||~7.4.0",
         "ext-bcmath": "*",
         "ext-curl": "*",
         "ext-dom": "*",