update example to use define_module

Author: rmorshea

examples/introduction.ipynb

@@ -692,7 +692,7 @@
    "source": [
     "print(\"Click the bars to see event data printed in Python 👇\")\n",
     "\n",
-    "chart = idom.widgets.import_module(\"chart\", \"chart.js\")\n",
+    "chart = idom.widgets.define_module(\"chart\", \"chart.js\")\n",
     "\n",
     "async def handle_event(event):\n",
     "    print(event)\n",