docs: fix search method return value handling in integration and example docs (#3208)

docs/integrations/langchain.mdx

@@ -64,7 +64,7 @@ Create functions to handle context retrieval, response generation, and addition
 def retrieve_context(query: str, user_id: str) -> List[Dict]:
     """Retrieve relevant context from Mem0"""
     memories = mem0.search(query, user_id=user_id)
-    serialized_memories = ' '.join([mem["memory"] for mem in memories])
+    serialized_memories = ' '.join([mem["memory"] for mem in memories.get('results', [])])
     context = [
         {
             "role": "system",