Fix typing imports in extraction usecase (langchain-ai#11402)

The person class here:
https://python.langchain.com/docs/use_cases/extraction#pydantic-1 has
attributes `dog_breed` and `dog_name` that use `Optional` from typing,
but it hasn't been imported. Fixed the import here

docs/extras/use_cases/extraction.ipynb

@@ -443,7 +443,7 @@
     }
    ],
    "source": [
-    "from typing import Sequence\n",
+    "from typing import Sequence, Optional\n",
     "from langchain.prompts import (\n",
     "    PromptTemplate,\n",
     "    ChatPromptTemplate,\n",