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/anthropic-iterative-search/anthropic_iterative_search/retriever.py

@@ -14,4 +14,4 @@ RETRIEVER_TOOL_NAME = "search"
 @tool
 def search(query):
     """Search with the retriever."""
-    return retriever.get_relevant_documents(query)
+    return retriever.invoke(query)