Update JupyterLite Altair example to latest API (#6226)

Author: philippjfr

lite/files/Getting_Started.ipynb

@@ -87,7 +87,7 @@
     ").properties(\n",
     "    width=250,\n",
     "    height=250\n",
-    ").add_selection(\n",
+    ").add_params(\n",
     "    brush\n",
     ")\n",
     "\n",