Bind the watchModelTypes's release function to this so it correctly removes the array observers

Author: bmac

packages/ember-extension-support/lib/data_adapter.js

@@ -302,9 +302,7 @@ export default EmberObject.extend({
 
     addArrayObserver(records, this, observer);
 
-    function release() {
-      removeArrayObserver(records, this, observer);
-    }
+    let release = () => removeArrayObserver(records, this, observer);
 
     return release;
   },