Fix missing comma in get_or_create_working_memory call

Added missing comma after model_name parameter.

Author: abrookins

python-recipes/context-engineering/notebooks/section-3-memory/01_working_memory_with_extraction_strategies.ipynb

@@ -239,7 +239,7 @@
         "# Retrieve working memory\n",
         "_, working_memory = await memory_client.get_or_create_working_memory(\n",
         "    session_id=session_id,\n",
-        "    model_name=\"gpt-4o\"\n",
+        "    model_name=\"gpt-4o\",\n",
         "    user_id=student_id,\n",
         ")\n",
         "\n",