support latest v6 of shopify api

Author: ryanmitchell

composer.json

@@ -12,7 +12,7 @@
     ],
     "require": {
         "pixelfear/composer-dist-plugin": "^0.1",
-        "shopify/shopify-api": "^5.1",
+        "shopify/shopify-api": "^6.1.1",
         "statamic/cms": "^4.56 || ^5.0"
     },
     "require-dev": {