Update master php enviroment

Signed-off-by: Joas Schilling <coding@schilljs.com>

composer.json

@@ -28,7 +28,7 @@
 			"composer/package-versions-deprecated": true
 		},
 		"platform": {
-			"php": "7.3"
+			"php": "7.4"
 		}
 	},
 	"scripts": {

composer.lock

@@ -5411,7 +5411,7 @@
     "platform": [],
     "platform-dev": [],
     "platform-overrides": {
-        "php": "7.3"
+        "php": "7.4"
     },
     "plugin-api-version": "2.2.0"
 }