fix: 🐛 Remove json_object from payload for non-json credentials (#1576)

* fix: 🐛 Remove json_object from payload for non-json credentials

* refactor: 💡 update new route logic for type specific attributes

* test: 💍 remove typeIn and use fillIn for json credential test

addons/api/addon/serializers/credential.js

@@ -25,6 +25,8 @@ export default class CredentialSerializer extends ApplicationSerializer {
         );
         delete serialized.attributes.json_object;
       }
+    } else {
+      delete serialized.attributes.json_object;
     }
 
     return serialized;