docs: fix broken link for the dappier retriever

docs/docs/integrations/retrievers/dappier.ipynb

@@ -31,7 +31,7 @@
    "source": [
     "# DappierRetriever\n",
     "\n",
-    "This will help you getting started with the Dappier [retriever](/docs/concepts/#retrievers). For detailed documentation of all DappierRetriever features and configurations head to the [API reference](https://python.langchain.com/en/latest/retrievers/langchain_dappier.retrievers.Dappier.DappierRetriever.html).\n",
+    "This will help you getting started with the Dappier [retriever](https://python.langchain.com/docs/concepts/retrievers/). For detailed documentation of all DappierRetriever features and configurations head to the [API reference](https://api.python.langchain.com/en/latest/retrievers/langchain_dappier.retrievers.Dappier.DappierRetriever.html).\n",
     "\n",
     "### Integration details\n",
     "\n",