Update app.py

app.py

@@ -400,7 +400,7 @@ components.html(
     """
     <script>
       function sendHeightWhenReady() {
-        const el = window.parent.document.getElementsByClassName('st-emotion-cache-b95f0i')[0];
+        const el = window.parent.document.getElementsByClassName('stMain')[0];
         if (el) {
           const height = el.scrollHeight;
           window.parent.parent.postMessage({ type: 'setHeight', height: height }, '*');