Require missing "doctrine/instantiator" dependency

Yea, well. If you are gonna use code from "doctrine/instantiator", you may declare that in composer.json.

Author: utietze

lib/internal/Magento/Framework/MessageQueue/composer.json

@@ -11,7 +11,8 @@
     ],
     "require": {
         "magento/framework": "*",
-        "php": "~7.1.3||~7.2.0||~7.3.0"
+        "php": "~7.1.3||~7.2.0||~7.3.0",
+        "doctrine/instantiator": "^1.0"
     },
     "autoload": {
         "psr-4": {