[Small upgrade] Allow document limit in AzureCognitiveSearchRetriever (#7690)

Multiple people have asked in #5081 for a way to limit the documents
returned from an AzureCognitiveSearchRetriever. This PR adds the `top_n`
parameter to allow that.


Twitter handle:
 [@UmerHAdil](twitter.com/umerHAdil)

docs/extras/modules/data_connection/retrievers/integrations/azure_cognitive_search.ipynb

@@ -91,7 +91,7 @@
    "metadata": {},
    "outputs": [],
    "source": [
-    "retriever = AzureCognitiveSearchRetriever(content_key=\"content\")"
+    "retriever = AzureCognitiveSearchRetriever(content_key=\"content\", top_k=10)"
    ]
   },
   {
@@ -111,6 +111,36 @@
    "source": [
     "retriever.get_relevant_documents(\"what is langchain\")"
    ]
+  },
+  {
+   "cell_type": "markdown",
+   "id": "72eca08e",
+   "metadata": {},
+   "source": [
+    "You can change the number of results returned with the `top_k` parameter. The default value is `None`, which returns all results. "
+   ]
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "097146c5",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "code",
+   "execution_count": null,
+   "id": "6d9963f5",
+   "metadata": {},
+   "outputs": [],
+   "source": []
+  },
+  {
+   "cell_type": "markdown",
+   "id": "dc120696",
+   "metadata": {},
+   "source": []
   }
  ],
  "metadata": {