fixed typo in assignment id getter

app.py

@@ -64,9 +64,9 @@ with demo:
     # Update the URL below to switch from Sandbox to real data collection
     def _submit(state, dummy):
         query = parse_qs(dummy[1:])
-        assert "assignmentId" in query, "No assignment ID provided, unable to submit"
-        state["assignmentId"] = query["assignmentId"]
-        url = "https://workersandbox.mturk.com/mturk/htmlSubmit"
+        assert "assignment_id" in query, "No assignment ID provided, unable to submit"
+        state["assignmentId"] = query["assignment_id"]
+        url = "https://workersandbox.mturk.com/mturk/externalSubmit"
         return requests.post(url, data=state)
 
     # Button event handlers