patch: deprecate (a)get_relevant_documents (#20477)

- `.get_relevant_documents(query)` -> `.invoke(query)`
- `.get_relevant_documents(query=query)` -> `.invoke(query)`
- `.get_relevant_documents(query, callbacks=callbacks)` ->
`.invoke(query, config={"callbacks": callbacks})`
- `.get_relevant_documents(query, **kwargs)` -> `.invoke(query,
**kwargs)`

---------

Co-authored-by: Erick Friis <erick@langchain.dev>

templates/cohere-librarian/cohere_librarian/rag.py

@@ -5,7 +5,7 @@ rag = CohereRagRetriever(llm=ChatCohere())
 
 
 def get_docs_message(message):
-    docs = rag.get_relevant_documents(message)
+    docs = rag.invoke(message)
     message_doc = next(
         (x for x in docs if x.metadata.get("type") == "model_response"), None
     )