docs: fix outdated link to langchain docs

Author: B4nan

sources/platform/integrations/langchain.md

@@ -118,7 +118,7 @@ LangChain is a standard interface through which you can interact with a variety
 
 ## Resources
 
-- <https://python.langchain.com/docs/get_started>
+- <https://python.langchain.com/docs/get_started/introduction/>
 - <https://python.langchain.com/docs/integrations/providers/apify>
 - <https://python.langchain.com/docs/integrations/tools/apify>
 - <https://python.langchain.com/docs/modules/model_io/llms/>