Fix exception occuring on Admin demotion (#1799)

* Fix an exception that occurred when demoting an Admin user
* Fix the response from the above request from returning a list instead of a dict
* Closes #1794

tests/api/v1/test_users.py

@@ -308,7 +308,7 @@ def test_api_user_patch_admin():
                 },
             )
             assert r.status_code == 200
-            user_data = r.get_json()["data"][0]
+            user_data = r.get_json()["data"]
             assert user_data["country"] == "US"
             assert user_data["verified"] is True
     destroy_ctfd(app)