docs: Fix broken link in summarization use-case (#16554)

- **Description:** Fix broken link to `StuffDocumentsChain`
- **Issue:** N/A
- **Dependencies:** None
- **Twitter handle:**
[@preetamdsouza](https://twitter.com/preetamdsouza)

docs/docs/use_cases/summarization.ipynb

@@ -224,7 +224,7 @@
    "source": [
     "## Option 1. Stuff\n",
     "\n",
-    "When we use `load_summarize_chain` with `chain_type=\"stuff\"`, we will use the [StuffDocumentsChain](/docs/modules/chains/document/stuff).\n",
+    "When we use `load_summarize_chain` with `chain_type=\"stuff\"`, we will use the [StuffDocumentsChain](https://api.python.langchain.com/en/latest/chains/langchain.chains.combine_documents.stuff.StuffDocumentsChain.html#langchain.chains.combine_documents.stuff.StuffDocumentsChain).\n",
     "\n",
     "The chain will take a list of documents, inserts them all into a prompt, and passes that prompt to an LLM:"
    ]